feat: per-setting sync table with dynamic 8-colour theme

Redesign the settings screen into uniform rows (sync icon | name | value):
dropdowns replace the chip pickers, every colour gets a reset to a canonical
default, a per-row sync icon toggles that setting's cross-device sync, and a
global switch flips all. Enabling a flag adopts this device's current value.

- AppSettings/SettingsStore: add text/bg/line colours, cache_months,
  month_view_paged, and the account-wide sync_flags map (+ DEFAULT_SYNC,
  effective-merge on pull)
- CalendarRepository.updateSettings: partial PUT of only the synced values plus
  the flag map (unsynced columns stay untouched server-side)
- Theme: fully dynamic — primary/accent tint, background/text/line drive
  background/onBackground/outline (matching web); today/divider/label unchanged
- add hide-profile (directory_hidden) to the profile block (parity with web/iOS)
- language + text/line contrast stay device-local

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/com/scarriffle/calendarr/ui/MainViewModel.kt

@@ -62,12 +62,12 @@ class MainViewModel @Inject constructor(
         _route.value = computeRoute()
     }
 
-    /** Pull appearance settings from the server, caching them locally. */
+    /** Pull settings from the server and merge them with local values honouring
+     *  each setting's sync flag (synced keys take the server value). */
     fun refreshSettings() {
         viewModelScope.launch {
             runCatching { repository.getSettings() }.onSuccess { s ->
-                settingsStore.saveSettings(s)
-                _settings.value = s
+                _settings.value = settingsStore.applyServerPull(s)
             }
         }
     }