refactor(gui): one-time launch elevation instead of "Run with admin"

Remove the per-page "Run with admin" buttons. At launch the GUI asks for the
password once (pkexec) and collects root-only data (SMART + dmidecode board/
BIOS/RAM) via the internal `collect-priv` command, caching it for the session;
Health and Inventory read that cache so they always show the full picture.

- core/elevation.py: pkexec collect + session cache
- cli: hidden `collect-priv` command (SMART + dmidecode -> JSON)
- health/inventory: use the elevation cache when present, else non-root
- main_window: collect at launch (config elevate_on_launch), then refresh
  Health/Inventory; falls back silently if cancelled/unavailable
- config: elevate_on_launch (default true)

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 = "0.3.1"
+version = "0.3.2"
 description = "Modular hardware monitoring & crash diagnostics for Linux gamers."
 readme = "README.md"
 requires-python = ">=3.11"