refactor: rename Chrome references to Chromium

- Rename hook file: 0060-install-chrome -> 0060-install-chromium
- Update all logs and comments to say "Chromium" instead of "Chrome"
- Rename chromeStatus -> chromiumStatus in daemon
- Update UI to show "Chromium Browser" instead of "Chrome Browser"
- Update documentation (readme.plan.md, readme.hints.md)

Note: Binary paths (/opt/chromium/chrome) remain as the actual
Chromium executable is named "chrome"

ecoos_daemon/mod.ts

@@ -5,7 +5,7 @@
  * Runs as root via systemd and orchestrates:
  * - Management UI on :3006
  * - Sway compositor as ecouser
- * - Chrome browser in kiosk mode
+ * - Chromium browser in kiosk mode
  */
 
 import { EcoDaemon } from './ts/daemon/index.ts';