auto-detect composer language from keyboard

adds a new expo-keyboard-language native module that reads the current
keyboard language on iOS (via first responder's textInputMode) and
Android (via InputMethodManager). iOS also gets real-time updates when
the keyboard language changes.

users opt in via Settings > Languages > "Automatically detect post
language from keyboard" (native only, marked experimental). when
enabled, the composer language tracks the keyboard language. users can
override per-session by selecting a language manually, and re-enable
auto mode via the "Automatic" item in the language menu.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/expo-keyboard-language/ios/ExpoKeyboardLanguage.podspec

@@ -0,0 +1,20 @@
+Pod::Spec.new do |s|
+  s.name           = 'ExpoKeyboardLanguage'
+  s.version        = '1.0.0'
+  s.summary        = 'Expo module to detect the current keyboard language'
+  s.description    = 'Expo module to detect the current keyboard language'
+  s.author         = ''
+  s.homepage       = 'https://github.com/bluesky-social/social-app'
+  s.platforms      = { :ios => '13.4' }
+  s.source         = { git: '' }
+  s.static_framework = true
+
+  s.dependency 'ExpoModulesCore'
+
+  s.pod_target_xcconfig = {
+    'DEFINES_MODULE' => 'YES',
+    'SWIFT_COMPILATION_MODE' => 'wholemodule'
+  }
+
+  s.source_files = "**/*.{h,m,mm,swift,hpp,cpp}"
+end