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/app/routers/features.py

@@ -0,0 +1,23 @@
+"""
+Public feature-flag read API — lets the authenticated frontend know
+which AI-powered sections to render.
+
+This is NOT the admin mutation endpoint (that's in ``admin.py`` and
+gated by ``require_admin``). Here we only expose the effective boolean
+state so the UI can hide things like the People view, Tags view, or
+text-search affordances when the underlying pipeline stage is off.
+"""
+from fastapi import APIRouter, Depends
+
+from app.dependencies import get_current_user
+from app.models.user import User
+from app.services.feature_flags import ALL_FLAGS, is_enabled
+
+router = APIRouter()
+
+
+@router.get("")
+async def get_enabled_features(_: User = Depends(get_current_user)):
+    """Return ``{flag_name: bool}`` for every known flag, reflecting
+    the currently effective value (admin override or YAML default)."""
+    return {name: is_enabled(name) for name in ALL_FLAGS}