feat v1.42.0: room settings — the third settings tier

- four-tier principle fixed in ARCHITECTURE: global > space > room >
  device, specific overrides general, unset inherits
- room.settings { fill_mode, temp_source, hum_source } with backend
  schema; pure roomFillModeOf + sourceValue (+2 test suites, 114)
- gear on room cards in the Plan editor opens Room settings: rename,
  re-area (current area included in the list), fill override (may opt
  out of glow darkness), explicit temp/hum source with a searchable
  device+entity dropdown; the same section in the creation dialog
- source feeds the room card, tooltip and temp fill; works for rooms
  without an HA area (user-feedback case #1)
- smoke_room_settings.mjs (10 checks); TESTING/CHANGELOG/ARCHITECTURE
  same-commit

docs/TESTING.md

@@ -140,6 +140,13 @@ Run the *core flows* (marked ★ below) in each environment at least once per mi
       (explicit ripple color still wins); off/white lights unchanged [auto]
 - [ ] Alarm pulse (v1.27.0): leak/smoke/gas/CO/siren in 'on' pulse a red ring over any
       display mode; clears on 'off'; unavailable never alarms [auto]; reduced-motion static
+- [ ] Room settings, tier 3 (v1.42.0): a gear on every room card in the Plan
+      editor opens Room settings (name, HA area incl. the current one, fill
+      override, temp/hum source); the creation dialog has the same section;
+      fill override repaints only that room (incl. opting OUT of the glow
+      darkness); a temp/hum source (device or entity) feeds the room card,
+      tooltip and temperature fill — works for rooms without an HA area;
+      renaming/rebinding an existing room now possible [auto]
 - [ ] PDF survival on rebinding (v1.41.2): rebind a marker with attached
       PDFs to another device — the server moves /files/<oldId>/ to the new id
       and the links keep opening; the old folder disappears (no orphans) [auto]