feat(config): add migration framework and config schema

Add simple SQL migration runner tracking applied migrations in
schema_migrations table. First migration creates:

- config schema
- config.adapters table (name, enabled, cadence_s, settings JSONB)
- config.api_keys table (alias, encrypted_value BYTEA)
- NOTIFY triggers for real-time config change detection
- Seeds NWS adapter row from current TOML config

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

sql/migrations/001_create_config_schema.sql

@@ -0,0 +1,64 @@
+-- Migration: 001_create_config_schema
+-- Creates the config schema with adapters and api_keys tables.
+-- Also seeds the NWS adapter row from current TOML config.
+
+-- Create config schema
+CREATE SCHEMA config;
+
+-- Adapters configuration table
+CREATE TABLE config.adapters (
+    name           TEXT PRIMARY KEY,
+    enabled        BOOLEAN NOT NULL DEFAULT true,
+    cadence_s      INTEGER NOT NULL,
+    settings       JSONB NOT NULL DEFAULT '{}'::jsonb,
+    paused_at      TIMESTAMPTZ,
+    updated_at     TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+-- API keys table (encrypted values)
+CREATE TABLE config.api_keys (
+    alias            TEXT PRIMARY KEY,
+    encrypted_value  BYTEA NOT NULL,
+    created_at       TIMESTAMPTZ NOT NULL DEFAULT now(),
+    rotated_at       TIMESTAMPTZ,
+    last_used_at     TIMESTAMPTZ
+);
+
+-- Notify function for config changes
+CREATE OR REPLACE FUNCTION config.notify_config_change()
+RETURNS trigger AS $$
+DECLARE
+    key_value TEXT;
+BEGIN
+    -- Handle different table structures
+    IF TG_TABLE_NAME = 'adapters' THEN
+        key_value := COALESCE(NEW.name, OLD.name, '');
+    ELSIF TG_TABLE_NAME = 'api_keys' THEN
+        key_value := COALESCE(NEW.alias, OLD.alias, '');
+    ELSE
+        key_value := '';
+    END IF;
+
+    PERFORM pg_notify('config_changed', TG_TABLE_NAME || ':' || key_value);
+    RETURN COALESCE(NEW, OLD);
+END;
+$$ LANGUAGE plpgsql;
+
+-- Trigger for adapters table
+CREATE TRIGGER adapters_notify
+    AFTER INSERT OR UPDATE OR DELETE ON config.adapters
+    FOR EACH ROW EXECUTE FUNCTION config.notify_config_change();
+
+-- Trigger for api_keys table
+CREATE TRIGGER api_keys_notify
+    AFTER INSERT OR UPDATE OR DELETE ON config.api_keys
+    FOR EACH ROW EXECUTE FUNCTION config.notify_config_change();
+
+-- Seed NWS adapter from current TOML config values
+INSERT INTO config.adapters (name, enabled, cadence_s, settings)
+VALUES (
+    'nws',
+    true,
+    60,
+    '{"states": ["ID", "OR", "WA", "MT", "WY", "UT", "NV"], "contact_email": "mj@k7zvx.com"}'::jsonb
+);