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/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1
-# Multi-stage build for the scopa stack (kaya backend + Sycamore/WASM
+# Multi-stage build for the tavolo stack (kaya backend + Sycamore/WASM
 # frontend). The Docker build context is the REPOSITORY ROOT (see
 # docker-compose.yml) so this single image assembles both parts:
 #
@@ -86,4 +86,4 @@ EXPOSE 8080
 HEALTHCHECK --interval=30s --timeout=3s --start-period=10s \
   CMD wget -q -O- http://127.0.0.1:8080/api/health || exit 1
 
-CMD ["granian", "scopa.app:app"]
+CMD ["granian", "tavolo.app:app"]