feat(git): add tag management and cherry-pick workflow

This update extends the Git backend and UI to support listing,
creating, deleting, and pushing tags. It also adds cherry-pick
commands with proper in-progress detection and conflict handling, and
prevents other operations while a cherry-pick is active.

- Add GitTag model, tag listing, and tag CRUD/push commands
- Implement cherry-pick start/continue/abort with status tracking
- Update UI to display tags and gate actions during cherry-pick

.claude/settings.local.json

@@ -79,7 +79,13 @@
       "Bash(rustfmt --edition 2024 --check src/git.rs)",
       "Bash(rustfmt --edition 2024 --check src/badge.rs)",
       "Bash(rustfmt --edition 2024 --check src/git.rs src/main.rs)",
-      "Bash(pkg-config --list-all)"
+      "Bash(pkg-config --list-all)",
+      "Bash(rustc --edition 2021 --crate-type lib -o /dev/null --emit=metadata src/git.rs)",
+      "Bash(rustc --edition 2021 --crate-type lib -o /dev/null --emit=metadata /mnt/d/Development/GitLite/src-tauri/src/git.rs)",
+      "Bash(rustc --edition 2021 --crate-type bin -o /dev/null --emit=metadata src/main.rs)",
+      "Bash(grep -B1 \"^error\\\\[E0432\\\\]\\\\|^error$\")",
+      "Bash(grep -v \"^--$\")",
+      "Bash(grep \"^error$\" -A2)"
     ]
   }
 }