feat: in-app updater with manual-download fallback

[chrisbendel]

Description

As a user, clicking the "new version available" takes you to the latest github release page, requires you to manually download the application and reinstall it. This should provide a path to update to the latest version directly in your application without re-downloading 🤞. There may be some work on your end to make sure things work properly with the signing keys/etc.

I am happy to iterate on this with some feedback on your end too @CyberTimon, thanks for taking the time to check this out!

Type of Change

• Bug fix
• New feature
• Breaking change
• Performance improvement
• Code refactoring
• Documentation update
• UI/UX improvement
• Build/CI or Dependency update

Changes Made

• Added tauri-plugin-updater (Rust + JS), registered desktop-only.
• Update badge now installs in-app (check → downloadAndInstall → relaunch); falls back to opening the releases page on any failure, so behavior is unchanged until updates are signed.
• Added desktop-scoped updater capability (excludes Android).
• Wired TAURI_SIGNING_PRIVATE_KEY/_PASSWORD env into the release build (no-op until secrets set).
• Added downloadingUpdate string across all 12 locales.

Not enabled by default — needs maintainer setup (one-time):

1. npx tauri signer generate → add private key + password as repo secrets.
2. Paste pubkey + set createUpdaterArtifacts: true and plugins.updater endpoint in tauri.conf.json.
3. macOS in-place update requires the app be code-signed (else Gatekeeper blocks the swap). Windows/AppImage work as-is; Android unaffected.

Until those land, CI builds exactly as before and the badge keeps opening the browser — zero regression.

Screenshots/Videos

Testing

• I have tested these changes locally and confirmed that they work as expected without issues

Test Configuration:

• OS:
• Hardware:

Checklist

• My code follows the project's code style
• I haven't added unnecessary AI-generated code comments
• My changes generate no new warnings or errors

Additional Notes

Updater config (createUpdaterArtifacts, plugins.updater.pubkey) is intentionally left out of tauri.conf.json — committing it without the signing key would fail the build. Happy to add it in this PR if you share a pubkey, or you can flip it on after merge.

AI Disclaimer:

• This PR is entirely AI-generated
• This PR is AI-generated but guided by a human
• This PR was handwritten with AI assistance (spell check, logic suggestions, error resolving)
• This PR contains only blood, sweat, and coffee (AI-free)

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Open items on you:

• Testing checkbox + OS/Hardware — left blank/unchecked. Check + fill once you run it locally. Don't claim tested if not.
• AI disclaimer — picked "AI-generated but guided by a human." Change if you disagree.
• Verify cargo check / build passes locally before checking the "no new warnings" box.