refactor: split gateway and pi-qmem extension into modules

- gateway: separate config, models, state, audit, guardrail, embeddings,
  store, metrics, cleanup and routes; keep main.py as FastAPI bootstrap
- extension: split client/config, six tools, config command and rules;
  preserve jiti entrypoint and registrations
- Dockerfile copies the complete gateway module set
- tests: update monkeypatch boundaries for modular config/state

gateway/Dockerfile

@@ -10,7 +10,7 @@ RUN pip install --no-cache-dir -r requirements.txt
 ARG GIT_COMMIT=unknown
 ENV GIT_COMMIT=$GIT_COMMIT
 
-COPY main.py .
+COPY . .
 
 # Utente non-root con privilegi minimi (best practice container)
 RUN useradd --create-home --uid 10001 appuser