Update frontend docs and significantly refactor dependency-check tooling.
- frontend: set supported version to "PVE 8.x / 9.x" and add info about --install/--status/--uninstall flags.
- Add new tools/pve/dependency-check copy.sh (installer wrapper).
- Rework tools/pve/dependency-check.sh: add CLI (install/status/uninstall), PVE version detection/validation, improved logging/colors, safer config parsing, more robust storage checks, validated tag handling (dep_ping/dep_tcp), portable TCP/ping checks, and wait/timeout helper.
- Improve applicator script handling (ignore list, avoid overwriting other hookscripts), update systemd units (PathExistsGlob, unit binding), and implement uninstall to remove assignments and installed files.
These changes harden lifecycle management and make installation/cleanup and runtime checks more robust and observable.
