Liquid Glass theme with in-app appearance switcher (#1337)

* Centralize UI theme colors into semantic ThemePalette tokens

Introduce AppTheme/ThemePalette (Utils/Theme.swift) with an environment
key and @ThemedPalette property wrapper, persisted via @AppStorage.
Views now resolve background/primary/secondary/accentBlue/alertRed/
divider tokens from the environment instead of computing colors inline,
removing the backgroundColor/textColor/secondaryTextColor prop-drilling
through the header, composer, and people-sheet hierarchy.

Matrix theme output is pixel-identical; this is groundwork for a
user-selectable theme switcher.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Add liquid glass theme with in-app appearance switcher

Add a .liquidGlass AppTheme alongside the matrix terminal theme,
selectable from a one-line APPEARANCE row in the app info sheet
(persisted via @AppStorage, applies live).

Liquid glass renders system fonts and colors over a subtle gradient
backdrop, with the header and composer floating as Liquid Glass panels
(real .glassEffect() on iOS/macOS 26, compiler-gated with an
ultraThinMaterial fallback for older SDKs). The message list scrolls
underneath the chrome via safe-area insets, and all sheets share the
same backdrop and surface language. The matrix theme is unchanged.

Details:
- Theme is threaded through ChatMessageFormatter so message
  AttributedStrings switch font design per theme; the per-message
  format cache gains a variant key so themes never serve each other's
  cached strings
- New palette tokens: accent (interactive tint) and locationAccent
  (geohash green), replacing scattered hardcoded greens/blues in the
  voice note, waveform, verification, and people-sheet views
- Header controls get full-height tap targets and the people count
  becomes a real Button (previously a tap gesture on the cluster)
- CommandSuggestionsView renders nothing when empty instead of a
  zero-height view that pushed the composer input off-center
- New appearance strings localized for all 29 catalog languages

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchatTests/ViewSmokeTests.swift

@@ -142,9 +142,6 @@ private struct ContentPeopleSheetHarness: View {
             isTextFieldFocused: $isTextFieldFocused,
             voiceRecordingVM: voiceRecordingVM,
             autocompleteDebounceTimer: $autocompleteDebounceTimer,
-            backgroundColor: .black,
-            textColor: .green,
-            secondaryTextColor: .gray,
             headerHeight: 44,
             onSendMessage: {},
             showImagePicker: $showImagePicker,
@@ -163,9 +160,6 @@ private struct ContentPeopleSheetHarness: View {
             isTextFieldFocused: $isTextFieldFocused,
             voiceRecordingVM: voiceRecordingVM,
             autocompleteDebounceTimer: $autocompleteDebounceTimer,
-            backgroundColor: .black,
-            textColor: .green,
-            secondaryTextColor: .gray,
             headerHeight: 44,
             onSendMessage: {},
             showMacImagePicker: $showMacImagePicker
@@ -335,8 +329,6 @@ struct ViewSmokeTests {
 
         _ = mount(
             MeshPeerList(
-                textColor: .green,
-                secondaryTextColor: .gray,
                 onTapPeer: { _ in },
                 onToggleFavorite: { _ in },
                 onShowFingerprint: { _ in }
@@ -344,8 +336,6 @@ struct ViewSmokeTests {
             .environmentObject(featureModels.peerListModel)
         )
         _ = MeshPeerList(
-            textColor: .green,
-            secondaryTextColor: .gray,
             onTapPeer: { _ in },
             onToggleFavorite: { _ in },
             onShowFingerprint: { _ in }
@@ -363,8 +353,6 @@ struct ViewSmokeTests {
 
         _ = mount(
             MeshPeerList(
-                textColor: .green,
-                secondaryTextColor: .gray,
                 onTapPeer: { _ in },
                 onToggleFavorite: { _ in },
                 onShowFingerprint: { _ in }
@@ -389,10 +377,7 @@ struct ViewSmokeTests {
                 messageText: Binding(
                     get: { messageText },
                     set: { messageText = $0 }
-                ),
-                textColor: .green,
-                backgroundColor: .black,
-                secondaryTextColor: .gray
+                )
             )
             .environmentObject(featureModels.privateConversationModel)
             .environmentObject(featureModels.locationChannelsModel)
@@ -539,8 +524,6 @@ struct ViewSmokeTests {
         let (viewModel, _, _) = makeSmokeViewModel()
         let featureModels = makeSmokeFeatureModels(for: viewModel)
         let geohashPeopleList = GeohashPeopleList(
-            textColor: .green,
-            secondaryTextColor: .gray,
             onTapPerson: {}
         )
         let truncatableMessage = BitchatMessage(