Add self-hosted PocketBase stack with auto-migrations

- docker-compose.yml: app + pocketbase services (PB internal to the network)
- pocketbase/: pinned PocketBase image, superuser bootstrap via env vars
- pb_migrations: production schema (collections, rules, public_users view)
  applied automatically on first boot
- pocketbase/pb_schema.json: schema export kept as reference
- README: full-stack deployment docs

README.md

@@ -36,11 +36,34 @@ against different PocketBase instances. For local dev, copy `.env.example` to
 
 ## Docker
 
+Single container (external PocketBase):
+
 ```sh
 docker build -t pokeshare .
 docker run -p 4321:4321 -e POCKETBASE_URL=https://pb.example.com pokeshare
 ```
 
+## Full stack (app + PocketBase)
+
+`docker-compose.yml` runs the app together with a PocketBase container. On
+first boot, PocketBase applies `pocketbase/pb_migrations/`, which creates the
+`users` profile fields, the `public_users` view, and the `mycards` and
+`friendships` collections with their API rules — no manual setup needed.
+
+```sh
+PB_SUPERUSER_EMAIL=admin@example.com PB_SUPERUSER_PASSWORD=changeme123 \
+    docker compose up --build
+```
+
+- The app listens on `4321`; PocketBase listens on `8090` (internal network,
+  admin UI at `/_/` if you expose it).
+- In Coolify, deploy as a **Docker Compose** resource and expose the `app`
+  service on your domain. Set `PB_SUPERUSER_*` in the environment variables.
+- Accounts are created from the PocketBase admin UI (public registration is
+  disabled by the migration).
+- To move existing data, use the PocketBase admin UI backups (Settings →
+  Backups) on the old instance and restore into `pb_data`.
+
 ## Structure
 
 - `src/pages/` — routes (`/`, `/search`, `/mycards`, `/card/[id]`,