feat: instant feedback button — creates Gitea issues with auto-labels

iOS:
- Subtle floating feedback button (bottom-left, speech bubble icon)
- Quick sheet: type → send → auto-creates Gitea issue
- Shows checkmark on success, auto-dismisses
- No friction — tap, type, done

Gateway:
- POST /api/feedback endpoint
- Auto-labels: bug/feature/enhancement + ios/web + fitness/brain/reader/podcasts
- Keyword detection for label assignment
- Creates issue via Gitea API with user name and source

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

gateway/server.py

@@ -25,6 +25,7 @@ from dashboard import (
     handle_set_connection, handle_pin, handle_unpin, handle_get_pinned,
 )
 from command import handle_command
+from feedback import handle_feedback
 from assistant import handle_assistant, handle_fitness_assistant, handle_brain_assistant
 from integrations.booklore import (
     handle_booklore_libraries, handle_booklore_import,
@@ -243,6 +244,12 @@ class GatewayHandler(ResponseMixin, BaseHTTPRequestHandler):
                 handle_command(self, user, body)
             return
 
+        if path == "/api/feedback":
+            user = self._require_auth()
+            if user:
+                handle_feedback(self, body, user)
+            return
+
         if path == "/api/assistant":
             user = self._require_auth()
             if user: