feat: replace Tauri dialog plugin with rfd integration

[qnixsynapse]

Describe Your Changes

Remove tauri-plugin-dialog dependency and its capability entry, adding our custom rfd (with xdg-desktop-portal dialog support on Linux) as a cross‑platform native file dialog library. Introduce open_dialog and save_dialog commands that expose file‑selection and save dialogs to the frontend, along with a DialogOpenOptions model for filter, directory, and multiple‑file support. Update the TauriDialogService to invoke these new commands instead of the removed plugin, ensuring a cleaner build and consistent dialog behaviour across desktop targets.

Fixes Issues

• Closes #6722
• Closes #

Self Checklist

• [ ] Added relevant comments, esp in complex areas
• [ ] Updated docs (for bug fixes / features)
• [ ] Created issues for follow-up changes or refactoring needed

[github-actions[bot]]

Barecheck - Code coverage report

Total: 29.93%

Your code coverage diff: 0.00% ▴

Uncovered files and lines

File	Lines
web-app/vite.config.web.ts	1-5, 8-12, 15, 17-18, 20-21, 33, 39-42, 44-59, 61-85, 87, 89-106, 108-109
web-app/src/services/dialog/tauri.ts	5, 7, 9-31, 33-41

[qnixsynapse]

@urmauur Can push the image attachment file chooser to tauri rfd fix here.

[urmauur]

@urmauur Can push the image attachment file chooser to tauri rfd fix here.

hey @qnixsynapse it's already on dev, u can pull latest dev

[qnixsynapse]

Already rebased and tested yesterday. Screencast_20251104_212314.webm

[Vanalite]

Tested on MacOS:

• Add images, doc
• Import GGUF