feat(updates): add system update endpoint and UI

Add automatic update functionality to allow users to update the
application directly from the UI without manual git commands.

Changes:
- Add POST /api/system/update endpoint that runs git pull and npm
  install
- Enhance useVersionCheck hook to fetch release information including
  changelog
- Update VersionUpgradeModal to display changelog and handle one-click
  updates
- Add update progress tracking with output display and error handling
- Bump version to 1.10.4

The update endpoint executes git checkout main, git pull, and npm
install, providing real-time output to the user. After successful
update, users are prompted to restart the server.

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@siteboon/claude-code-ui",
-  "version": "1.10.3",
+  "version": "1.10.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@siteboon/claude-code-ui",
-      "version": "1.10.3",
+      "version": "1.10.4",
       "license": "MIT",
       "dependencies": {
         "@anthropic-ai/claude-agent-sdk": "^0.1.29",