Decouple sidecar versioning from app versioning

Sidecar now has its own version (1.0.0) and release lifecycle:
- Sidecar tags: sidecar-v1.0.0, sidecar-v1.0.1, etc.
- App tags: v0.2.x (unchanged)
- Sidecar workflow triggers only on python/** changes or manual dispatch
- App release no longer bumps python/pyproject.toml

Sidecar version tracked via sidecar-version.txt in app data dir:
- resolve_sidecar_path() reads version from file instead of CARGO_PKG_VERSION
- download_sidecar() fetches latest sidecar-v* release from Gitea API
- check_sidecar_update() compares local vs remote sidecar versions
- Version file written after successful download

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

.gitea/workflows/release.yml

@@ -47,9 +47,6 @@ jobs:
           # Update src-tauri/Cargo.toml (match version = "x.y.z" in [package] section)
           sed -i "s/^version = \"${CURRENT}\"/version = \"${NEW_VERSION}\"/" src-tauri/Cargo.toml
 
-          # Update python/pyproject.toml
-          sed -i "s/^version = \".*\"/version = \"${NEW_VERSION}\"/" python/pyproject.toml
-
           echo "new_version=${NEW_VERSION}" >> $GITHUB_OUTPUT
           echo "tag=v${NEW_VERSION}" >> $GITHUB_OUTPUT
 
@@ -58,7 +55,7 @@ jobs:
           BUILD_TOKEN: ${{ secrets.BUILD_TOKEN }}
         run: |
           NEW_VERSION="${{ steps.bump.outputs.new_version }}"
-          git add package.json src-tauri/tauri.conf.json src-tauri/Cargo.toml python/pyproject.toml
+          git add package.json src-tauri/tauri.conf.json src-tauri/Cargo.toml
           git commit -m "chore: bump version to ${NEW_VERSION} [skip ci]"
           git tag "v${NEW_VERSION}"