Rename the app from scopa to tavolo

The platform now hosts multiple card games, with scopone scientifico as
the first one. Rename the brand wherever it is not a game rule:

- move the Python package to server/src/tavolo and update imports
- rename the Postgres database/user, OIDC issuer path, client id and
  Redis key prefixes to tavolo (clean break: existing pgdata volumes and
  live games are not migrated)
- rename the Cargo package to tavolo-web and set the page title to Tavolo
- update docs and the Docker image path to woggioni/tavolo

The scopa game term (clearing the table) in the engine, state and web UI
is intentionally left untouched.

server/.env.example

@@ -1,15 +1,15 @@
 # Postgres
 POSTGRES_HOST=localhost
 POSTGRES_PORT=5432
-POSTGRES_DB=scopa
-POSTGRES_USER=scopa
-POSTGRES_PASSWORD=scopa
-DATABASE_URL=postgres://scopa:scopa@localhost:5432/scopa
+POSTGRES_DB=tavolo
+POSTGRES_USER=tavolo
+POSTGRES_PASSWORD=tavolo
+DATABASE_URL=postgres://tavolo:tavolo@localhost:5432/tavolo
 
 # OIDC (mock-oauth2-server in dev; it does not validate clients, so any
 # client id/secret works. For a real IdP like Keycloak, use its values here.)
-OIDC_ISSUER=http://localhost:8180/scopa
-OIDC_CLIENT_ID=scopa
+OIDC_ISSUER=http://localhost:8180/tavolo
+OIDC_CLIENT_ID=tavolo
 OIDC_CLIENT_SECRET=dev-secret
 OIDC_REDIRECT_URI=http://localhost:8080/auth/callback