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"

isobuild/config/hooks/normal/0050-setup-ecouser.hook.chroot

@@ -1,5 +1,5 @@
 #!/bin/sh
-# Create ecouser for running Sway and Chrome
+# Create ecouser for running Sway and Chromium
 
 set -e