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>

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to RigDoctor are recorded here. Format follows
 (`MAJOR.MINOR.PATCH`, pre-1.0). `__version__` and `pyproject.toml` must match the git
 release tag (so the auto-updater, D18, can compare versions).
 
+## [0.3.2] - 2026-05-21
+### Changed
+- Replaced the per-page "Run with admin" buttons with a **single password prompt at launch**
+  (`pkexec`): the GUI collects root-only data (SMART + dmidecode board/BIOS/RAM) once and
+  caches it for the session, so Health and Inventory always show the full picture. Falls back
+  to non-root if cancelled/unavailable; disable via `elevate_on_launch = false`.
+
 ## [0.3.1] - 2026-05-21
 ### Fixed
 - Changelog/release notes now **render Markdown** instead of showing raw `#`/`**` markup —