feat: runtime feature flags, upload/download, RAW decoding

Adds Redis-backed feature flags for vision stages with admin UI toggles
and manual backfill trigger, photo upload and download routers with
frontend upload modal, and rawpy-based RAW decoding with JPEG fallback
for misnamed DNGs. Fixes pgvector serialization, is_trashed filter, and
naive-datetime bind in incremental duplicate regrouping; bumps Celery
time limits on regroup tasks beyond the 5-minute default.

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

backend/requirements.txt

@@ -18,7 +18,12 @@ flower==2.0.1
 
 # Image processing
 # pyvips==2.2.1  # Optional - having compatibility issues, using Pillow as fallback
-# rawpy==0.19.0  # Optional - numpy compatibility issues, using Pillow as fallback
+rawpy==0.26.1               # RAW decoder (CR2/NEF/ARW/DNG/…). cp312 wheels
+                            # ship with libraw bundled; the older 0.19 pin
+                            # had numpy 2.x incompatibilities — 0.26 is fine
+                            # with our numpy 1.26. iPhone ProRAW-style DNGs
+                            # that aren't real RAW still fail here; thumbs.py
+                            # falls back to opening them as JPEG in that case.
 pillow==10.2.0
 pillow-heif==0.15.0
 imagehash==4.3.1  # perceptual hash for duplicate detection