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/templates/_frame_name_edit.html

@@ -0,0 +1,9 @@
+<span class="frame-name-view" id="frame-name-view">
+  <span id="frame-name-text">{{ frame.name or ("Frame " ~ frame.id) }}</span>
+  <button type="button" class="frame-name-pencil" id="frame-name-pencil" title="Rename frame" aria-label="Rename frame">&#9998;</button>
+</span>
+<span class="frame-name-edit" id="frame-name-edit-row" style="display: none;">
+  <input type="text" id="frame-name-input" maxlength="64" value="{{ frame.name }}">
+  <button type="button" class="btn-inline" id="frame-name-save">Save</button>
+  <button type="button" class="btn-inline secondary" id="frame-name-cancel">Cancel</button>
+</span>