fix: use supabase/postgres image for auth schema compatibility

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -1,16 +1,16 @@
 services:
-  # PostgreSQL database
+  # Supabase PostgreSQL (includes auth schema + extensions)
   db:
-    image: postgres:16-alpine
+    image: supabase/postgres:15.8.1.060
     restart: unless-stopped
     environment:
       POSTGRES_PASSWORD: ${DB_PASSWORD:-postgres}
-      POSTGRES_DB: calctext
+      POSTGRES_DB: postgres
     volumes:
       - calctext-db:/var/lib/postgresql/data
-      - ./supabase/migrations:/docker-entrypoint-initdb.d
+      - ./supabase/migrations:/docker-entrypoint-initdb.d/migrations
     healthcheck:
-      test: pg_isready -U postgres
+      test: pg_isready -U postgres -d postgres
       interval: 5s
       timeout: 5s
       retries: 10
@@ -27,7 +27,7 @@ services:
       GOTRUE_API_PORT: 9999
       API_EXTERNAL_URL: ${SITE_URL:-http://localhost:5173}/auth
       GOTRUE_DB_DRIVER: postgres
-      GOTRUE_DB_DATABASE_URL: postgres://postgres:${DB_PASSWORD:-postgres}@db:5432/calctext?sslmode=disable
+      GOTRUE_DB_DATABASE_URL: postgres://postgres:${DB_PASSWORD:-postgres}@db:5432/postgres?sslmode=disable
       GOTRUE_SITE_URL: ${SITE_URL:-http://localhost:5173}
       GOTRUE_URI_ALLOW_LIST: ${SITE_URL:-http://localhost:5173}/**
       GOTRUE_DISABLE_SIGNUP: 'false'
@@ -46,7 +46,7 @@ services:
       db:
         condition: service_healthy
     environment:
-      PGRST_DB_URI: postgres://postgres:${DB_PASSWORD:-postgres}@db:5432/calctext
+      PGRST_DB_URI: postgres://postgres:${DB_PASSWORD:-postgres}@db:5432/postgres
       PGRST_DB_SCHEMAS: public
       PGRST_DB_ANON_ROLE: anon
       PGRST_JWT_SECRET: ${JWT_SECRET}
@@ -61,7 +61,7 @@ services:
         condition: service_healthy
     environment:
       PORT: 4000
-      DATABASE_URL: postgres://postgres:${DB_PASSWORD:-postgres}@db:5432/calctext
+      DATABASE_URL: postgres://postgres:${DB_PASSWORD:-postgres}@db:5432/postgres
       JWT_SECRET: ${JWT_SECRET}
 
   # Web frontend (nginx + static files)