feat(schema): add USGS quake adapter and CENTRAL_QUAKE stream

Migration 006 seeds:
- config.adapters row for usgs_quake (60s cadence, PNW bbox)
- config.streams row for CENTRAL_QUAKE (7d retention)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

sql/migrations/006_add_usgs_quake_adapter.sql

@@ -0,0 +1,23 @@
+-- Migration: 006_add_usgs_quake_adapter
+-- Seeds USGS earthquake adapter configuration and CENTRAL_QUAKE stream.
+
+-- Seed USGS quake adapter row
+INSERT INTO config.adapters (name, enabled, cadence_s, settings)
+VALUES (
+    'usgs_quake',
+    true,
+    60,
+    jsonb_build_object(
+        'region', jsonb_build_object(
+            'north', 49.5,
+            'south', 31.0,
+            'east', -102.0,
+            'west', -124.5
+        ),
+        'feed', 'all_hour'
+    )
+);
+
+-- Seed CENTRAL_QUAKE stream row (7d retention)
+INSERT INTO config.streams (name, max_age_s, max_bytes)
+VALUES ('CENTRAL_QUAKE', 604800, 1073741824);