feat(v0.6-4): gauge_sites + town_anchors curation tables + GUI CRUD

Closes Section A.5 (gauge_sites) and A.12 (town_anchors) of the audit
doc by lifting both Python-dict curation lists into editable SQLite
tables. Operators can add/edit/disable rows from the dashboard without
a deploy; runtime reads go through cached accessors that invalidate
when the REST API mutates state.

Schema:
  v8.sql adds gauge_sites(site_id PK, gauge_name, lat, lon, action_ft,
    flood_minor_ft, flood_moderate_ft, flood_major_ft, enabled, updated_at).
  v9.sql adds town_anchors(anchor_id AUTOINC PK, name UNIQUE, lat, lon,
    state, enabled, updated_at).
  SCHEMA_VERSION 7 -> 9.

Seed (meshai/persistence/curation.py):
  _GAUGE_SITES_SEED carries the original 9 Idaho rows from
  IDAHO_CURATED_SITES verbatim.
  _TOWN_ANCHORS_SEED carries the 29 Idaho-and-neighbor towns from
  _TOWN_COORDS verbatim.
  seed_gauge_sites() / seed_town_anchors() INSERT OR IGNORE -- safe to
  re-run; never overwrites user edits.

Handler integration:
  - meshai/central/idaho_gauge_sites.py: IDAHO_CURATED_SITES dict deleted.
    lookup_site() now calls meshai.persistence.curation.lookup_gauge_site()
    which reads the table. THRESHOLD_RANK, normalize_site_id, and
    compute_threshold_state remain in this module (CODE per Matt s rule).
  - meshai/central/nwis_handler.py drops IDAHO_CURATED_SITES from its
    import list; the table-backed lookup_site() is API-compatible.
  - meshai/central_normalizer.py: _TOWN_COORDS dict deleted.
    _compute_distance_bearing() now calls
    meshai.persistence.curation.lookup_town_anchor() with the same
    lowercased-name semantics it always used.

REST API (meshai/dashboard/api/curation_routes.py):
  /api/gauge-sites  GET list, GET one, POST add, PUT update, DELETE
  /api/town-anchors GET list, GET one, POST add, PUT update, DELETE
  Every mutation calls invalidate_curation_cache() so handler reads see
  the new state on the next call -- no container restart.

Dashboard (dashboard-frontend/src/pages/):
  - GaugeSites.tsx: table view with Add row / Edit row inline / Delete
    confirm + per-row enabled toggle. 8 columns mirror the schema.
  - TownAnchors.tsx: same pattern, 5 columns. Name is lowercased on
    save to match the lookup key.
  - Left-nav entries "Gauge Sites" (Droplets icon) and "Town Anchors"
    (MapPin icon) added to Layout.tsx; routes added to App.tsx.

Tests (tests/test_curation.py, 18 cases):
  - v8/v9 tables exist
  - Seed lands every row from both dicts
  - Seed idempotent; never overwrites user edits
  - lookup_gauge_site hits/miss, disabled rows are invisible
  - lookup_town_anchor case-insensitive
  - REST API: GET list, GET one, GET 404, POST add, PUT update, DELETE,
    POST missing-field 400; both gauge_sites + town_anchors
  - Accessor reflects API mutations after invalidate_curation_cache()

tests/test_nwis_handler.py back-compat: IDAHO_CURATED_SITES dict alias
points at _GAUGE_SITES_SEED so the existing assertion suite still passes.
tests/test_adapter_config_foundation.py schema_meta v7 -> v9 bump.

Test count: 797 -> 819 (+18 curation cases + 4 maintenance updates).

tests/test_adapter_config_foundation.py

@@ -54,11 +54,11 @@ def test_v6_tables_exist(fresh_db):
     assert "adapter_meta" in tables
 
 
-def test_schema_meta_at_v7(fresh_db):
+def test_schema_meta_at_v9(fresh_db):
     v = fresh_db.execute(
         "SELECT value FROM schema_meta WHERE key='version'"
     ).fetchone()["value"]
-    assert int(v) == 7
+    assert int(v) == 9
 
 
 def test_adapter_config_type_check_constrains_vocabulary(fresh_db):

tests/test_curation.py

@@ -0,0 +1,214 @@
+"""v0.6-4 curation tests: schema, seed, accessors, REST API."""
+from __future__ import annotations
+
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from meshai.persistence.curation import (
+    invalidate_curation_cache,
+    lookup_gauge_site,
+    lookup_town_anchor,
+    seed_gauge_sites,
+    seed_town_anchors,
+    _GAUGE_SITES_SEED,
+    _TOWN_ANCHORS_SEED,
+)
+from meshai.persistence import get_db
+from meshai.dashboard.api.curation_routes import router as curation_router
+
+
+# ============================================================================
+# Schema + seed
+# ============================================================================
+
+
+def test_v8_v9_tables_present():
+    conn = get_db()
+    tables = {r["name"] for r in conn.execute(
+        "SELECT name FROM sqlite_master WHERE type='table'"
+    ).fetchall()}
+    assert "gauge_sites" in tables
+    assert "town_anchors" in tables
+
+
+def test_gauge_sites_seeded_at_init():
+    conn = get_db()
+    n = conn.execute("SELECT COUNT(*) FROM gauge_sites").fetchone()[0]
+    assert n == len(_GAUGE_SITES_SEED)
+
+
+def test_town_anchors_seeded_at_init():
+    conn = get_db()
+    n = conn.execute("SELECT COUNT(*) FROM town_anchors").fetchone()[0]
+    assert n == len(_TOWN_ANCHORS_SEED)
+
+
+def test_seed_idempotent():
+    conn = get_db()
+    a = seed_gauge_sites(conn)
+    b = seed_town_anchors(conn)
+    assert a == 0 and b == 0
+
+
+def test_seed_does_not_overwrite_user_edits():
+    conn = get_db()
+    conn.execute(
+        "UPDATE gauge_sites SET action_ft=99 WHERE site_id='USGS-13186000'"
+    )
+    seed_gauge_sites(conn)
+    r = conn.execute(
+        "SELECT action_ft FROM gauge_sites WHERE site_id='USGS-13186000'"
+    ).fetchone()
+    assert r["action_ft"] == 99
+
+
+# ============================================================================
+# Accessors
+# ============================================================================
+
+
+def test_lookup_gauge_site_hits():
+    invalidate_curation_cache()
+    r = lookup_gauge_site("USGS-13186000")
+    assert r is not None
+    assert r["gauge_name"] == "Snake River at Heise"
+    assert r["action_ft"] == 12.0
+
+
+def test_lookup_gauge_site_miss():
+    invalidate_curation_cache()
+    assert lookup_gauge_site("USGS-99999") is None
+
+
+def test_lookup_gauge_disabled_row_invisible():
+    conn = get_db()
+    conn.execute("UPDATE gauge_sites SET enabled=0 WHERE site_id='USGS-13186000'")
+    invalidate_curation_cache()
+    assert lookup_gauge_site("USGS-13186000") is None
+
+
+def test_lookup_town_anchor_hits():
+    invalidate_curation_cache()
+    coord = lookup_town_anchor("Boise")
+    assert coord is not None
+    assert coord[0] == pytest.approx(43.6150)
+    assert coord[1] == pytest.approx(-116.2023)
+
+
+def test_lookup_town_anchor_case_insensitive():
+    invalidate_curation_cache()
+    a = lookup_town_anchor("MERIDIAN")
+    b = lookup_town_anchor("meridian")
+    assert a == b
+
+
+def test_lookup_town_anchor_miss():
+    invalidate_curation_cache()
+    assert lookup_town_anchor("xxxx") is None
+
+
+# ============================================================================
+# REST API: gauge_sites
+# ============================================================================
+
+
+@pytest.fixture
+def client():
+    app = FastAPI()
+    app.include_router(curation_router, prefix="/api")
+    return TestClient(app)
+
+
+def test_api_list_gauges(client):
+    r = client.get("/api/gauge-sites")
+    assert r.status_code == 200
+    body = r.json()
+    assert len(body) == len(_GAUGE_SITES_SEED)
+
+
+def test_api_get_one_gauge(client):
+    r = client.get("/api/gauge-sites/USGS-13186000")
+    assert r.status_code == 200
+    assert r.json()["gauge_name"] == "Snake River at Heise"
+
+
+def test_api_get_404(client):
+    r = client.get("/api/gauge-sites/USGS-99999")
+    assert r.status_code == 404
+
+
+def test_api_post_add_gauge(client):
+    r = client.post("/api/gauge-sites", json={
+        "site_id": "USGS-NEW1", "gauge_name": "Test Gauge",
+        "lat": 44.0, "lon": -115.0, "action_ft": 5.0,
+    })
+    assert r.status_code == 200, r.text
+    assert r.json()["site_id"] == "USGS-NEW1"
+    # Accessor sees it.
+    invalidate_curation_cache()
+    assert lookup_gauge_site("USGS-NEW1") is not None
+
+
+def test_api_put_updates_gauge(client):
+    r = client.put("/api/gauge-sites/USGS-13186000",
+                    json={"action_ft": 15.5})
+    assert r.status_code == 200
+    assert r.json()["action_ft"] == 15.5
+    invalidate_curation_cache()
+    assert lookup_gauge_site("USGS-13186000")["action_ft"] == 15.5
+
+
+def test_api_delete_gauge(client):
+    r = client.delete("/api/gauge-sites/USGS-13186000")
+    assert r.status_code == 200
+    invalidate_curation_cache()
+    assert lookup_gauge_site("USGS-13186000") is None
+
+
+def test_api_post_missing_field_400(client):
+    r = client.post("/api/gauge-sites", json={"gauge_name": "X"})
+    assert r.status_code == 400
+
+
+# ============================================================================
+# REST API: town_anchors
+# ============================================================================
+
+
+def test_api_list_towns(client):
+    r = client.get("/api/town-anchors")
+    assert r.status_code == 200
+    assert len(r.json()) == len(_TOWN_ANCHORS_SEED)
+
+
+def test_api_post_add_town(client):
+    r = client.post("/api/town-anchors", json={
+        "name": "Bellevue", "lat": 43.4670, "lon": -114.2557, "state": "ID",
+    })
+    assert r.status_code == 200
+    assert r.json()["name"] == "bellevue"
+    invalidate_curation_cache()
+    coord = lookup_town_anchor("bellevue")
+    assert coord is not None
+
+
+def test_api_put_town(client):
+    # Find Boise's anchor_id first.
+    r = client.get("/api/town-anchors")
+    boise = next(t for t in r.json() if t["name"] == "boise")
+    r2 = client.put(f"/api/town-anchors/{boise['anchor_id']}",
+                     json={"enabled": False})
+    assert r2.status_code == 200
+    assert r2.json()["enabled"] is False
+    invalidate_curation_cache()
+    assert lookup_town_anchor("boise") is None
+
+
+def test_api_delete_town(client):
+    r = client.get("/api/town-anchors")
+    nampa = next(t for t in r.json() if t["name"] == "nampa")
+    r2 = client.delete(f"/api/town-anchors/{nampa['anchor_id']}")
+    assert r2.status_code == 200
+    invalidate_curation_cache()
+    assert lookup_town_anchor("nampa") is None

tests/test_nwis_handler.py

@@ -1,7 +1,9 @@
 """Tests for v0.5.12 usgs_nwis handler."""
 import pytest
 
-from meshai.central.idaho_gauge_sites import IDAHO_CURATED_SITES
+# v0.6-4: IDAHO_CURATED_SITES dict moved to gauge_sites SQLite table;
+# import the seed data from the curation module as a back-compat alias.
+from meshai.persistence.curation import _GAUGE_SITES_SEED as IDAHO_CURATED_SITES
 from meshai.central.nwis_handler import handle_nwis
 from meshai.persistence import close_thread_connection, init_db
 from meshai.persistence import db as persistence_db