Move frame name/mode into the page header; Calendar gets its own tab

Frame name (pencil-icon inline edit) and the Photos/Calendar mode
selector now live in the page header, shared across all four per-frame
pages instead of being buried in the Configuration form -- so renaming
a frame or flipping its mode no longer requires navigating to a
specific tab first.

Calendar settings move out of a conditionally-hidden card on the
Configuration tab into their own dedicated tab (new /frames/{id}/
calendar route), visually greyed out when the frame is in Photos mode
but still fully usable so calendar settings can be configured ahead of
switching modes. Also wires the week-start setting into the UI for the
first time (the column/backend support landed earlier but had no
control anywhere).

server/app/routers/frame_pages.py

@@ -1,7 +1,7 @@
-"""The per-frame HTML pages: Photos (/frames/{id}), Configuration, and
-Stats tabs, all inside the sidebar app shell. Data loading happens
-client-side against /api/frames/{id}/... (routers/api_frames.py); these
-routes just authorize and render the scaffold."""
+"""The per-frame HTML pages: Photos (/frames/{id}), Configuration,
+Calendar, and Stats tabs, all inside the sidebar app shell. Data loading
+happens client-side against /api/frames/{id}/... (routers/api_frames.py);
+these routes just authorize and render the scaffold."""
 
 from __future__ import annotations
 
@@ -73,8 +73,20 @@ def frame_config_page(frame_id: int, request: Request, db: Session = Depends(get
         default_palette_rgb=DEFAULT_PALETTE_RGB,
         palette_to_hex=palette_to_hex,
         display_mode_labels=DISPLAY_MODE_LABELS,
+    )
+
+
+WEEK_START_LABELS = {0: "Monday", 1: "Tuesday", 2: "Wednesday", 3: "Thursday",
+                     4: "Friday", 5: "Saturday", 6: "Sunday"}
+
+
+@router.get("/frames/{frame_id}/calendar", response_class=HTMLResponse)
+def frame_calendar_page(frame_id: int, request: Request, db: Session = Depends(get_db)):
+    return _frame_page(
+        request, db, frame_id, "frame_calendar.html", "calendar",
         calendar_views=CALENDAR_VIEW_LABELS,
         calendar_users=_calendar_users_for_frame(db, frame_id),
+        week_start_labels=WEEK_START_LABELS,
     )