fix(feed): compose footer above keyboard, tab spacing, FAB position

- Composer footer (attach / counter / fee bar) now rides with the
  keyboard on both platforms: KeyboardAvoidingView behavior is
  "padding" on iOS and "height" on Android. Previously behavior was
  undefined on Android, and the global softwareKeyboardLayoutMode:"pan"
  setting lifted the whole screen — leaving the footer hidden below
  the keyboard.
- Feed tab strip (Подписки / Для вас / В тренде) had zero horizontal
  breathing room — three equal-width Pressables flush to the edges.
  Added 12px outer paddingHorizontal + 10px gap + slightly bigger
  paddingVertical. The active indicator is now 32px wide (was 48) so
  it sits under the label instead of underlining two words.
- Floating compose FAB pinned to the right edge with a 14px inset
  (was 18). Vertical offset tightened from +70 to +62 above the
  safe-area inset — closer to the NavBar top edge while still clear
  of the icons.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

client-app/app/(app)/compose.tsx

@@ -198,7 +198,7 @@ export default function ComposeScreen() {
   return (
     <KeyboardAvoidingView
       style={{ flex: 1, backgroundColor: '#000000' }}
-      behavior={Platform.OS === 'ios' ? 'padding' : undefined}
+      behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
     >
       {/* Header */}
       <View