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/main.py

@@ -11,7 +11,7 @@ import os
 
 from app.config import settings
 from app.database import init_db
-from app.routers import photos, folders, heaps, tags, discard, library, search, auth, admin, sharing
+from app.routers import photos, folders, heaps, tags, discard, library, search, auth, admin, sharing, upload, download, features
 from app.services.scanner import start_initial_scan, bootstrap_default_source_root
 from app.services.cleanup import cleanup_data_integrity
 
@@ -95,6 +95,9 @@ app.include_router(tags.router, prefix="/api/v1/tags", tags=["tags"])
 app.include_router(discard.router, prefix="/api/v1/discard", tags=["discard"])
 app.include_router(library.router, prefix="/api/v1/library", tags=["library"])
 app.include_router(search.router, prefix="/api/v1/photos/search", tags=["search"])
+app.include_router(upload.router, prefix="/api/v1/upload", tags=["upload"])
+app.include_router(download.router, prefix="/api/v1/download", tags=["download"])
+app.include_router(features.router, prefix="/api/v1/features", tags=["features"])
 
 @app.get("/")
 async def root():