feat(updater): macOS auto-update via Tauri Updater

- tauri-plugin-updater wired into lib.rs with pubkey + GitHub Releases
  endpoint in tauri.conf.json; updater:default capability granted
- AppUpdater.tsx: on macOS, the download button now invokes the updater
  plugin (check + downloadAndInstall) which downloads the signed
  .app.tar.gz, verifies the minisign signature against the bundled
  pubkey, replaces /Applications/Psysonic.app, and relaunches. Windows
  and Linux keep the existing "download DMG/EXE/AppImage via reqwest
  then point to the folder" flow
- CI: pass TAURI_SIGNING_PRIVATE_KEY + _PASSWORD to tauri-action so the
  .sig files are produced alongside the update bundles
- New generate-manifest job (after build-macos-windows) runs
  scripts/generate-update-manifest.js which downloads the .sig files
  from the release, assembles latest.json for darwin-aarch64 and
  darwin-x86_64, and uploads it back as a release asset

Windows will be added to latest.json once the Certum cert is active.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -122,10 +122,32 @@ jobs:
           APPLE_API_ISSUER: ${{ secrets.APPLE_API_ISSUER }}
           APPLE_API_KEY: ${{ secrets.APPLE_API_KEY }}
           # APPLE_API_KEY_PATH comes from the previous step via $GITHUB_ENV
+          # Tauri Updater signing — produces .sig files alongside the update bundles
+          TAURI_SIGNING_PRIVATE_KEY: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY }}
+          TAURI_SIGNING_PRIVATE_KEY_PASSWORD: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY_PASSWORD }}
         with:
           releaseId: ${{ needs.create-release.outputs.release_id }}
           args: ${{ matrix.settings.args }}
 
+  generate-manifest:
+    needs: [create-release, build-macos-windows]
+    runs-on: ubuntu-24.04
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v5
+      - name: generate latest.json
+        env:
+          VERSION: ${{ needs.create-release.outputs.package_version }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: node scripts/generate-update-manifest.js
+      - name: upload latest.json to release
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          VERSION=${{ needs.create-release.outputs.package_version }}
+          gh release upload "app-v${VERSION}" latest.json --clobber
+
   build-linux:
     needs: create-release
     permissions: