features: add commit and push option to git commit window

- Add split button with dropdown in commit dialog supporting both
  "Commit" and "Commit and Push" actions
- Pass folderId through gitCommit/gitPush API calls so backend emits
  events that the folder window can receive for toast notifications
- Update Tauri git_commit and git_push commands to accept folder_id
  parameter with window label fallback for cross-window compatibility
- Wrap commit page with GitCredentialProvider for push authentication
- Keep commit window open when push fails so user can see the error
- Add i18n translations for all 10 locales

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

src/i18n/messages/en.json

@@ -1009,6 +1009,7 @@
     "commitDialog": {
       "toasts": {
         "commitCompleted": "Code commit completed",
+        "pushFailed": "Push failed",
         "committedFiles": "Committed {count, plural, one {# file} other {# files}}",
         "addedToVcs": "Added to VCS",
         "addToVcsFailed": "Failed to add to VCS",
@@ -1050,6 +1051,7 @@
       "commitMessage": "Commit message",
       "commitMessagePlaceholder": "Enter commit message...",
       "commitButton": "Commit ({count})",
+      "commitAndPushButton": "Commit and Push ({count})",
       "head": "HEAD",
       "workingTree": "Working Tree",
       "clickFileToDiff": "Click a file name to view diff",