calendar_render.py's _build_* functions now take a real target box and pick font sizes/margins from three discrete size tiers (nearest pixel-area fit) instead of always laying out at full panel size and resizing after the fact -- a calendar widget placed smaller than the full panel gets an actually-legible layout instead of shrunk text. Month view falls back to agenda below the smallest tier, where 7 columns can no longer stay readable. The old photo-inlay split (inlay_region/_content_region/_paste_inlay) is deleted along with it -- arbitrary widget placement already subsumes what a fixed half-panel split did, and every call site has passed photo_inlay=None since the Phase 2 cutover. Also adds HTTP-level test coverage for GET .../preview/calendar, which had none before this -- it's what caught a stale photo_inlay kwarg left over from the _build signature change that would have TypeError'd on every request.