fix(install,tools): address PR 376 review findings

- first_time_install.sh: add _clone_rpi_rgb() wrapper so retry() cleans
  up any partial rpi-rgb-led-matrix-master dir before each clone attempt
- first_time_install.sh: use apt-get -o DPkg::Lock::Timeout=180 so apt
  handles lock contention natively instead of relying solely on flock TOCTOU check
- install_dependencies_apt.py: pass DPkg::Lock::Timeout=180 to apt-get
  install to avoid failing when unattended-upgrades holds the lock
- install_dependencies_apt.py: add type annotations to all public helpers
- api_v3.py: fix install_plugin_requirements to read plugin_manager from
  api_v3 blueprint attribute instead of the always-None module variable
- tools.html: loadGitInfo() now checks r.ok before parsing JSON and
  surfaces d.status === 'error' with the server's message in the panel

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web_interface/templates/v3/partials/tools.html

@@ -274,6 +274,7 @@
                     return;
                 }
 
+
                 const dirtyBadge = d.dirty
                     ? '<span class="inline-flex items-center px-2 py-0.5 rounded text-xs font-medium bg-yellow-100 text-yellow-800">dirty</span>'
                     : '<span class="inline-flex items-center px-2 py-0.5 rounded text-xs font-medium bg-green-100 text-green-800">clean</span>';