Widget system Phase 1: per-type render/action modules

New app/widgets/ package (photos.py, calendar.py, whiteboard.py, plus
the WIDGET_TYPES registry) -- the widget-system analogue of
routers/device.py's old RENDERERS/ADVANCE_RENDERERS/BACK_RENDERERS,
generalized from "one mode owns the whole panel" to "each widget renders
into its own region and responds to named button actions." Each module
exposes render(db, frame, widget, target_w, target_h) -> Image.Image
(never raises -- a widget's own fetch hiccup falls back to a small
placeholder rather than taking the whole panel's render down) and an
ACTIONS registry for NEXT/BACK button assignment.

Supporting changes needed to give the widget modules something to call,
all mechanical/behavior-preserving for every existing caller:

- image_pipeline.py: render_panel(regions, ...) generalizes render_frame's
  tail (paste, enhance once, overlay once, quantize once, pack once) from
  one photo to N regions -- not a restructuring, since calendar mode's
  photo-inlay feature already pastes a second composed image onto the
  canvas before that single shared pipeline runs.
- photo_queue.py: advance_forced/back_forced/remove_from_rotation/
  get_current take an explicit `frame` param now that `cfg` won't always
  be the Frame itself once photo-queue state moves to PhotoWidgetConfig
  -- caught a real latent bug while doing this: get_current was reading
  refresh_interval_s off `cfg`, but that's a frame-level wake-cadence
  setting, not something that becomes per-widget, so it now reads that
  off `frame` explicitly instead.
- routers/common.py: list_assets/fetch_source_and_faces take album_id/
  display_mode directly instead of a whole Frame (both only ever read
  that one attribute off it); new get_or_refresh_*_for_widget siblings
  of the existing calendar/weather/tasks/whiteboard cache helpers, read/
  writing the new per-widget config tables -- the Frame-scoped originals
  are untouched and still what routers/device.py's actual dispatch calls
  until the Phase 2 cutover.

26 new tests (95 total): render_panel size/placement/orientation
coverage, and per-widget-type render/action tests (unconfigured ->
placeholder, a fetch failure -> placeholder not a crash, actions mutate
the right state). Full suite passes; diff-reviewed to confirm
device.py's actual RENDERERS dispatch and the old Frame-scoped
get_or_refresh_* bodies are unchanged, so this is safe to deploy on its
own despite being step 1 of a two-step cutover (see the project plan on
why the *next* step, not this one, has to ship atomically).

server/app/routers/device.py

@@ -97,10 +97,10 @@ def _render_photos_mode(db: Session, frame: Frame, request: Request, manage: dic
     if not _frame_configured(frame):
         return _setup_placeholder(frame, request, manage=manage)
     client = immich_client_for(frame)
-    assets = list_assets(client, frame)
+    assets = list_assets(client, frame.album_id)
 
     with frame_locked(db, frame.id) as locked:
-        photo_queue.get_current(locked, assets, in_quiet_hours=quiet_hours.in_quiet_hours(locked))
+        photo_queue.get_current(locked, assets, locked, in_quiet_hours=quiet_hours.in_quiet_hours(locked))
         asset_id = locked.current_asset_id
 
     return render_asset(client, frame, asset_id, manage=manage)
@@ -109,10 +109,10 @@ def _render_photos_mode(db: Session, frame: Frame, request: Request, manage: dic
 def _advance_photos_mode(db: Session, frame: Frame, manage: dict | None) -> bytes:
     require_configured(frame)
     client = immich_client_for(frame)
-    assets = list_assets(client, frame)
+    assets = list_assets(client, frame.album_id)
 
     with frame_locked(db, frame.id) as locked:
-        photo_queue.advance_forced(locked, assets)
+        photo_queue.advance_forced(locked, assets, locked)
         asset_id = locked.current_asset_id
 
     return render_asset(client, frame, asset_id, manage=manage)
@@ -121,10 +121,10 @@ def _advance_photos_mode(db: Session, frame: Frame, manage: dict | None) -> byte
 def _back_photos_mode(db: Session, frame: Frame, manage: dict | None) -> bytes:
     require_configured(frame)
     client = immich_client_for(frame)
-    assets = list_assets(client, frame)
+    assets = list_assets(client, frame.album_id)
 
     with frame_locked(db, frame.id) as locked:
-        photo_queue.back_forced(locked, assets)
+        photo_queue.back_forced(locked, assets, locked)
         asset_id = locked.current_asset_id
 
     return render_asset(client, frame, asset_id, manage=manage)
@@ -168,9 +168,9 @@ def _render_calendar_mode(db: Session, frame: Frame, request: Request, manage: d
     if inlay_wanted and _frame_configured(frame):
         try:
             client = immich_client_for(frame)
-            assets = list_assets(client, frame)
+            assets = list_assets(client, frame.album_id)
             with frame_locked(db, frame.id) as locked:
-                photo_queue.get_current(locked, assets, in_quiet_hours=quiet_hours.in_quiet_hours(locked))
+                photo_queue.get_current(locked, assets, locked, in_quiet_hours=quiet_hours.in_quiet_hours(locked))
                 asset_id = locked.current_asset_id
             if asset_id:
                 jpeg_bytes = client.download_asset_preview(asset_id)