You are helping build a SPEC4AI Studio phone app that uses Docker database
services. Here is the complete technical context:

## Architecture
- Phone WebView apps call fetch('/api/v1/gateway') with route 'services/proxy'
- The phone's MCP server forwards this to the SPEC4AI bridge on the Mac
- The bridge's handleServiceProxy() looks up the service in its registry
- For PostgREST services, it sets Accept-Profile and Content-Profile headers
  for per-app schema isolation, then forwards to http://127.0.0.1:3100
- PostgREST auto-generates REST API from PostgreSQL tables

## Database Helper Function (REQUIRED in every app using DB)
```javascript
const APP_ID = 'custom.YOUR_APP_NAME'; // Must match spec.json id

async function db(method, path, body) {
  const r = await fetch('/api/v1/gateway', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      route: 'services/proxy',
      params: { service: 'api', method, path, body, app_id: APP_ID }
    })
  });
  const data = await r.json();
  if (!data.ok) throw new Error(data.error?.message || 'DB error');
  return data.result;
}
```

## PostgREST Query Syntax
- GET    /table?column=eq.value     — filter rows
- GET    /table?order=col.desc      — sort
- GET    /table?limit=10&offset=20  — paginate
- GET    /table?col=ilike.*term*    — search (case-insensitive)
- GET    /table?col=gt.10           — greater than
- GET    /table?col=in.(a,b,c)      — in list
- GET    /table?select=id,name      — select columns
- POST   /table + JSON body         — insert row
- PATCH  /table?id=eq.5 + JSON body — update matching rows
- DELETE /table?id=eq.5             — delete matching rows

## Migration Rules (in spec.json services.api.migrations)
1. Always use CREATE SCHEMA IF NOT EXISTS app_<name>;
2. Always use CREATE TABLE IF NOT EXISTS
3. Schema name = "app_" + app_id after last dot (e.g., custom.foo → app_foo)
4. MUST grant permissions after creating tables:
   GRANT USAGE ON SCHEMA app_<name> TO web_anon;
   GRANT ALL ON ALL TABLES IN SCHEMA app_<name> TO web_anon;
   GRANT USAGE ON ALL SEQUENCES IN SCHEMA app_<name> TO web_anon;
5. For schema evolution, use ALTER TABLE with exception handling:
   DO $$ BEGIN
     ALTER TABLE app_<name>.table ADD COLUMN col type DEFAULT val;
     EXCEPTION WHEN duplicate_column THEN NULL;
   END $$;
6. Migrations must be idempotent — they run on every deploy

## Common Mistakes to Avoid
- NEVER connect to PostgreSQL directly from phone JavaScript
- NEVER hardcode localhost:3100 in phone app code — always use the gateway
- NEVER forget GRANT statements — PostgREST returns empty without them
- NEVER use schema names that don't start with "app_"
- ALWAYS include app_id in proxy requests — without it, schema isolation breaks
- ALWAYS use IF NOT EXISTS in migrations — they run repeatedly

## spec.json Services Section Template
```json
{
  "services": {
    "api": {
      "type": "postgrest",
      "migrations": [
        "CREATE SCHEMA IF NOT EXISTS app_YOURAPP;",
        "CREATE TABLE IF NOT EXISTS app_YOURAPP.tablename (...);",
        "GRANT USAGE ON SCHEMA app_YOURAPP TO web_anon;",
        "GRANT ALL ON ALL TABLES IN SCHEMA app_YOURAPP TO web_anon;",
        "GRANT USAGE ON ALL SEQUENCES IN SCHEMA app_YOURAPP TO web_anon;"
      ]
    }
  }
}
```