feat(system-reset): add system reset and factory reset feature

- Add FACTORY_RESET_ON_STARTUP and ENABLE_FACTORY_RESET config settings
- Create app/utils/system_reset.py with core reset logic (wipe DB + files, reimport)
- Create app/api/system_reset.py with admin-only API endpoints
- Create app/views/system_reset.py with admin-only UI view
- Create frontend/templates/system_reset.html with confirmation dialogs
- Auto-reset on startup when FACTORY_RESET_ON_STARTUP=true
- Re-import uses watch folder mechanism for re-ingestion
- Register routers in API and views init files
- Add i18n keys and SETTING_METADATA entries
- Add nav links in base.html (desktop + mobile)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/templates/base.html

@@ -177,6 +177,11 @@
                   <a href="/admin/backup" role="menuitem" class="flex items-center px-4 py-2 text-sm text-gray-700 hover:bg-gray-100">
                     <i class="fas fa-database w-4 mr-2 text-green-600" aria-hidden="true"></i> {{ _("nav.backup_restore") }}
                   </a>
+                  {% if enable_factory_reset %}
+                  <a href="/admin/system-reset" role="menuitem" class="flex items-center px-4 py-2 text-sm text-red-600 hover:bg-red-50">
+                    <i class="fas fa-skull-crossbones w-4 mr-2 text-red-500" aria-hidden="true"></i> {{ _("nav.system_reset") }}
+                  </a>
+                  {% endif %}
                   <a href="/admin/audit-logs" role="menuitem" class="flex items-center px-4 py-2 text-sm text-gray-700 hover:bg-gray-100">
                     <i class="fas fa-shield-halved w-4 mr-2 text-indigo-500" aria-hidden="true"></i> Audit Logs
                   </a>
@@ -445,6 +450,11 @@
                   <a href="/admin/backup" class="block px-3 py-3 rounded-md text-base font-medium text-gray-700 hover:text-gray-900 hover:bg-gray-50">
                     <i class="fas fa-database mr-2 text-green-500" aria-hidden="true"></i> {{ _("nav.backup_restore") }}
                   </a>
+                  {% if enable_factory_reset %}
+                  <a href="/admin/system-reset" class="block px-3 py-3 rounded-md text-base font-medium text-red-600 hover:text-red-800 hover:bg-red-50">
+                    <i class="fas fa-skull-crossbones mr-2 text-red-500" aria-hidden="true"></i> {{ _("nav.system_reset") }}
+                  </a>
+                  {% endif %}
                   <a href="/status" class="block px-3 py-3 rounded-md text-base font-medium text-gray-700 hover:text-gray-900 hover:bg-gray-50"
                      {% if request and request.url.path == '/status' %}aria-current="page"{% endif %}>
                     <i class="fas fa-circle-dot mr-2 text-gray-400" aria-hidden="true"></i> {{ _("nav.status") }}