Admin can now upload a png/jpg event photo (SPEC §8 exception added):
- new image-upload admin field kind with live preview, uploading via
POST /api/admin/upload (fenja-only, type + 5MB validation);
- files stored under data/uploads (gitignored, BIFROST_UPLOAD_DIR
overridable) and served by GET /uploads/[file] with a traversal guard.
Reworks the /pulse event card: the greeting moved inside a taller box, the
"next gathering" label sits above the date + title, and the photo renders
as a top-right background that blends into the indigo via gradient masks.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
