feat(chat): автозаглавная буква в начале предложений при наборе

TextCapitalization.sentences для композера, подписи к вложениям
и шторки редактирования сообщения.

lib/frontend/screens/chats/chat/view/composer_input.dart

@@ -273,6 +273,8 @@ class ComposerInputBar extends StatelessWidget {
                                         ),
                                         maxLines: null,
                                         keyboardType: TextInputType.multiline,
+                                        textCapitalization:
+                                            TextCapitalization.sentences,
                                         textAlignVertical:
                                             TextAlignVertical.center,
                                         contextMenuBuilder: contextMenuBuilder,

lib/frontend/screens/chats/chat_screen.dart

@@ -7605,6 +7605,7 @@ class _EditMessageSheetState extends State<_EditMessageSheet> {
             autofocus: true,
             minLines: 1,
             maxLines: 6,
+            textCapitalization: TextCapitalization.sentences,
             style: TextStyle(color: cs.onSurface),
             contextMenuBuilder: (ctx, state) =>
                 widget.contextMenuBuilder(_controller, ctx, state),

lib/frontend/widgets/attachment/attachment_sheet.dart

@@ -832,6 +832,7 @@ class _AttachmentSheetState extends State<AttachmentSheet> {
                   controller: _captionCtrl,
                   style: TextStyle(color: cs.onSurface, fontSize: 15),
                   cursorColor: cs.primary,
+                  textCapitalization: TextCapitalization.sentences,
                   decoration: InputDecoration(
                     isCollapsed: true,
                     border: InputBorder.none,