feat: enhance feedback form with image upload, user/project context, and scene graph (#113)

* feat: enhance feedback form with image upload, user/project context, and scene graph

- Add invisible drag-and-drop zone that reveals on hover+drag with dashed border overlay
- Multi-image upload (max 5, max 5MB each) to Supabase Storage feedback-images bucket
- Subtle attach button + thumbnail previews with remove on hover
- Auto-capture authenticated user email/name from Better Auth session
- Pass projectId from editor context
- Snapshot scene graph (nodes + rootNodeIds) on submit
- DB migration adds user_email, user_name, project_id, images (jsonb), scene_graph (jsonb) columns
- Storage bucket + RLS policies for public read / service role write

* refactor: use existing user_id FK instead of denormalized email/name columns

Removed user_email and user_name — the user_id already links to the users table.
Simpler schema, no data duplication.

* fix: guard against undefined in removeImage

* refactor: direct Supabase Storage upload via signed URLs

Bypass Vercel's 4.5MB serverless body-size limit by uploading images
directly from the client to Supabase Storage.

- New createImageUploadUrls server action generates signed upload URLs
- Client PUTs files directly to Supabase (no bytes through Vercel)
- submitFeedback now receives only image paths, not FormData with files
- No migration changes needed (existing RLS policies support signed URLs)

* fix: remove relative class that broke dialog centering

twMerge was replacing the Dialog's fixed positioning with relative,
pushing the dialog to the bottom of the viewport.

---------

Co-authored-by: Anton Pascal <anton-pascal@users.noreply.github.com>

supabase/migrations/20260223020000_feedback_images_and_context.sql

@@ -0,0 +1,20 @@
+-- Add image upload, project context, and scene graph to feedback
+ALTER TABLE feedback
+  ADD COLUMN IF NOT EXISTS project_id text,
+  ADD COLUMN IF NOT EXISTS images jsonb,
+  ADD COLUMN IF NOT EXISTS scene_graph jsonb;
+
+-- Create feedback-images storage bucket (public read, service-role write)
+INSERT INTO storage.buckets (id, name, public)
+VALUES ('feedback-images', 'feedback-images', true)
+ON CONFLICT (id) DO NOTHING;
+
+-- Allow public read on feedback-images bucket
+CREATE POLICY "Public read feedback images"
+  ON storage.objects FOR SELECT
+  USING (bucket_id = 'feedback-images');
+
+-- Allow service role (and authenticated users) to upload
+CREATE POLICY "Service role upload feedback images"
+  ON storage.objects FOR INSERT
+  WITH CHECK (bucket_id = 'feedback-images');