feat(gui): add a "Check for updates" button to the sidebar

Force an immediate version check instead of waiting for the 30-minute poll.
Reuses the background update check; no-op while awaiting restart after an update.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "rigdoctor"
-version = "0.1.1"
+version = "0.2.0"
 description = "Modular hardware monitoring & crash diagnostics for Linux gamers."
 readme = "README.md"
 requires-python = ">=3.11"