FIX: Complete CodeMirror integration with native search, replace, and keyboard shortcuts

- Replace custom search/replace implementation with native CodeMirror extensions
- Add proper keyboard shortcut support: Ctrl+F, Ctrl+H, Ctrl+/, Ctrl+Space, etc.
- Fix browser shortcut conflicts by preventing defaults only when editor is focused
- Integrate autocompletion and comment toggle functionality
- Fix file name truncation in file manager grid to use text wrapping
- Add comprehensive keyboard shortcuts help panel for users
- Update i18n translations for editor buttons (Download, Replace, Replace All)
- Unify text and code file editing under single CodeMirror instance
- Add proper SSH HMAC algorithms for better compatibility

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/backend/ssh/file-manager.ts

@@ -224,7 +224,7 @@ app.post("/ssh/file_manager/ssh/connect", async (req, res) => {
         "aes256-cbc",
         "3des-cbc",
       ],
-      hmac: ["hmac-sha2-256", "hmac-sha2-512", "hmac-sha1", "hmac-md5"],
+      hmac: ["hmac-sha2-256-etm@openssh.com", "hmac-sha2-512-etm@openssh.com", "umac-128-etm@openssh.com", "hmac-sha2-256", "hmac-sha2-512", "hmac-sha1", "hmac-md5"],
       compress: ["none", "zlib@openssh.com", "zlib"],
     },
   };