Add a static image widget (PNG/JPEG/GIF/BMP/WEBP/TIFF/PDF upload)

A new widget type showing a single user-uploaded image with no live
upstream to poll -- decoded once at upload time (PDF's first page via
pypdfium2, BSD-3-Clause/Apache-2.0, no copyleft exposure) into plain RGB
PNG bytes, then composed per a crop/stretch/letterbox display mode like
the photos widget.

server/app/widgets/static_image.py

@@ -0,0 +1,35 @@
+"""Static image widget: shows whatever image the user last uploaded
+(routers/api_widgets.py's api_widget_static_upload already decoded
+PNG/JPEG/GIF/PDF/etc. into plain RGB PNG bytes at upload time, see
+app/image_upload.py and models.StaticWidgetConfig) -- no live upstream
+to fetch, so render() is just a decode + compose_into, the simplest of
+every widget type's render().
+
+No button actions -- there's nothing to advance/back/check for a fixed
+uploaded image."""
+
+from __future__ import annotations
+
+import io
+
+from PIL import Image
+from sqlalchemy.orm import Session
+
+from ..image_pipeline import compose_into
+from ..models import Frame, StaticWidgetConfig, Widget
+from ._shared import placeholder_image
+
+ACTIONS: dict = {}
+ACTION_LABELS: dict[str, str] = {}
+
+
+def render(db: Session, frame: Frame, widget: Widget, target_w: int, target_h: int,
+          is_normal_wake: bool = True) -> Image.Image:
+    """is_normal_wake is unused -- see app/widgets/whiteboard.py's
+    identical note; every widget type's render() shares one call
+    signature regardless of which ones actually care."""
+    cfg = db.get(StaticWidgetConfig, widget.id)
+    if not cfg.image:
+        return placeholder_image(target_w, target_h, ["Static image widget", "not configured yet"])
+    source = Image.open(io.BytesIO(cfg.image)).convert("RGB")
+    return compose_into(source, faces=None, target_w=target_w, target_h=target_h, display_mode=cfg.display_mode)