feat(phase-0): stability hardening — search path fix, auto-migrations, graceful shutdown, health endpoint

- Remove SET search_path from db.py and migration SQL (Supabase uses public schema)
- Add migrate.py with tracking table for forward-only SQL migrations
- Add entrypoint.sh: waits for DB, runs migrations, then starts app
- Copy 01-schema.sql + zz-seed.sql to worker/src/migrations/
- Add health.py: /health endpoint (200/503) with DB connectivity + scheduler staleness checks
  - /stats endpoint with keyword/ad/notification counts
- Rewrite main.py shutdown sequence: signal handler, 5s grace for scheduler, ordered cleanup
- Update Dockerfile: HEALTHCHECK directive, entrypoint, COPY migrations
- Update docker-compose.yml: stop_grace_period=15s, healthcheck config, env vars
- Add aiohttp>=3.9 to requirements.txt for health server

docs/phase-0/task-search-path-fix.md

@@ -0,0 +1,101 @@
+# Task: search_path consistency fix
+
+## Description
+
+There is a mismatch between the database schema configuration and where tables actually live:
+
+**In `db.py` (`_init_connection`):**
+```python
+await conn.execute("SET search_path TO willhaben_tracker")
+```
+
+**But in `supabase-migration.sql`:**
+- The migration file has `SET search_path TO willhaben_tracker;` but the actual tables were created in `public` schema (not `willhaben_tracker`) when manually applied.
+- The original local Supabase migrations used `public` schema.
+
+This creates two problems:
+1. If a connection does NOT run `_init_connection`, queries to bare table names (`SELECT FROM keywords`) fail with "relation does not exist".
+2. Tools that connect directly (pgAdmin, DBeaver, PostgREST) won't find the tables without explicit schema qualification or their own search_path config.
+
+## Decision: Remove custom schema, use `public` for everything
+
+Since Supabase uses `public` by default and all existing tools/GRANTs in `post-boot.sql` target `public`, we simplify by removing the `willhaben_tracker` schema entirely.
+
+### Rationale
+
+| Factor | Custom Schema (`willhaben_tracker`) | Public Schema |
+|--------|--------------------------------------|---------------|
+| Supabase Studio compatibility | Requires manual config | ✅ Works out of box |
+| PostgREST/Kong access | Needs search_path override | ✅ Default |
+| Direct pgAdmin/DBeaver access | Must set schema per-connection | ✅ Always visible |
+| Grant statements in post-boot.sql | ❌ Targets wrong schema | ✅ Already correct |
+| Code changes needed | Minimal (remove one line) | Minimal |
+
+## Architecture
+
+```
+BEFORE (broken):
+  db.py init: SET search_path TO willhaben_tracker
+  tables live in: public.keywords, public.ads, ...
+  Result: queries fail because search_path != table location
+
+AFTER (fixed):
+  db.py init: REMOVED (no custom search_path)
+  tables live in: public.keywords, public.ads, ...
+  Result: all connections find tables via default 'public' schema
+```
+
+## Implementation Details
+
+### 1. Remove `SET search_path` from `db.py`
+
+**Current:**
+```python
+async def _init_connection(conn: asyncpg.Connection) -> None:
+    await conn.execute("SET search_path TO willhaben_tracker")
+```
+
+**After:**
+```python
+# Removed entirely - using default public schema
+```
+
+The `_init_connection` function can be removed, and `init=_init_connection` removed from `create_pool()`. Alternatively keep the callback but make it a no-op for future use:
+
+```python
+async def _init_connection(conn: asyncpg.Connection) -> None:
+    # Reserved for future connection-level settings (e.g., timezone)
+    pass
+```
+
+### 2. Clean up migration files
+
+- Remove `SET search_path TO willhaben_tracker;` from `supabase-migration.sql` / `01-schema.sql`
+- Ensure all tables are explicitly created in the default schema (no need for prefix — that's already what happens)
+
+### 3. Update `post-boot.sql` grants if needed
+
+Current grants already target `public`:
+```sql
+GRANT USAGE ON SCHEMA public TO supabase_admin;
+```
+→ ✅ Already correct, no change needed.
+
+### 4. Add schema qualification to migration file (defensive)
+
+To be explicit and future-proof, the migration can qualify the schema:
+
+```sql
+-- Instead of implicit public.keywords
+CREATE TABLE IF NOT EXISTS public.keywords (...)
+```
+
+This is optional but makes it unambiguous where tables live. For simplicity we'll keep implicit `public` since that's the default everywhere.
+
+## Acceptance Criteria
+
+- [ ] Removing `_init_connection` from db.py does not break any query (all table names resolve correctly)
+- [ ] Connecting to the database via pgAdmin/DBeaver shows all tables without schema configuration
+- [ ] The healthcheck endpoint DB check works without custom search_path
+- [ ] No "relation does not exist" errors in worker logs after redeploy
+- [ ] Migration SQL file no longer references `willhaben_tracker` schema