add general file upload support with pool-aware tus client

- add "uploadFile" i18n key (en, zh-CN, zh-TW)
- introduce putFileToPool for tus upload with X-FilePool header
- add ComposeLogic.pickGeneralFile for arbitrary files
- extend uploadAttachment to support poolId override
- add toolbar button for general file upload

Signed-off-by: Texas0295 <kimura@texas0295.top>

lib/widgets/post/compose_toolbar.dart

@@ -25,6 +25,10 @@ class ComposeToolbar extends HookConsumerWidget {
       ComposeLogic.pickVideoMedia(ref, state);
     }
 
+    void pickGeneralFile() {
+      ComposeLogic.pickGeneralFile(ref, state);
+    }
+
     void addAudio() {
       ComposeLogic.recordAudioMedia(ref, state, context);
     }
@@ -96,6 +100,12 @@ class ComposeToolbar extends HookConsumerWidget {
                 icon: const Icon(Symbols.mic),
                 color: colorScheme.primary,
               ),
+              IconButton(
+                onPressed: pickGeneralFile,
+                tooltip: 'uploadFile'.tr(),
+                icon: const Icon(Symbols.file_upload),
+                color: colorScheme.primary,
+              ),
               IconButton(
                 onPressed: linkAttachment,
                 icon: const Icon(Symbols.attach_file),