v0.22.1: dockerize defaults, harden error handling, fix test discovery

- config.py: defaults to localhost/localhost, AMQP to rabbitmq, secret
  path to /run/secrets, RAG_MAX_VECTORS from env
- rag.py: EMBED_URL default to localhost
- app.py: syslog handler wrapped in try/except
- routers/completions.py: db.close() in try/finally
- db.py: PRAGMA journal_mode = WAL
- amqp.py: subscription append before try for reconnect safety
- tests/conftest.py: add project root to sys.path for test discovery

amqp.py

@@ -43,6 +43,8 @@ async def subscribe(exchange: str, routing_keys: list[str], handler) -> None:
     if ch is None:
         log.error("cannot subscribe — no AMQP channel")
         return
+    # Track subscription before attempting so reconnect catches it even if this try fails
+    _subscriptions.append((exchange, routing_keys, handler))
     try:
         queue = await ch.declare_queue("", exclusive=True)
         ex = await ch.get_exchange(exchange)
@@ -58,7 +60,6 @@ async def subscribe(exchange: str, routing_keys: list[str], handler) -> None:
                     log.exception("AMQP handler error for %s %s", exchange, msg.routing_key)
 
         await queue.consume(_dispatch)
-        _subscriptions.append((exchange, routing_keys, handler))
     except Exception:
         log.exception("AMQP subscribe failed for %s %s", exchange, routing_keys)