fix(gateway): enforce request body size limits

config/default.yaml

@@ -16,6 +16,8 @@ server:
     serve: false
   localhost: true
   port: 18800
+  # Maximum inbound HTTP request body size (bytes) for webhooks/Gmail push.
+  max_request_body_bytes: 1048576
 
 models:
   # ── Model tiers ────────────────────────────────────────────────────
@@ -45,6 +47,12 @@ models:
     # auth_mode: auto                  # auto | api_key | oauth (provider-specific)
     # use_oauth: false                 # compat alias for auth_mode: oauth
     # supports_audio: false            # Override native audio detection per tier
+  fast:
+    provider: anthropic
+    model: claude-haiku-4-5-20251001
+  complex:
+    provider: anthropic
+    model: claude-opus-4-6-20250715
   local:
     provider: ollama
     model: glm-4.7-flash