feat(admin): GitHub repo button in the sidebar footer (#778)

Adds a subtle 'View PicPeak on GitHub' link in the admin sidebar footer
(next to the version/storage widgets), so admins can reach the repo —
star it, browse source, report an issue — from anywhere in the dashboard,
not just the setup screen.

- Centralizes the repo URL as `repoUrl` in utils/githubReleaseUrl.ts
  (githubReleaseUrl now derives from it) so the org URL lives in one place.
- target=_blank + rel=noopener noreferrer; EN + DE i18n
  (`admin.viewOnGithub`); dark-mode aware, matches the muted footer style.

frontend/src/components/admin/AdminSidebar.tsx

@@ -15,11 +15,13 @@ import {
   Workflow,
   PanelLeftClose,
   PanelLeftOpen,
+  Github,
 } from 'lucide-react';
 import { useQuery } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import { settingsService } from '../../services/settings.service';
 import { VersionInfo } from './VersionInfo';
+import { repoUrl } from '../../utils/githubReleaseUrl';
 import { usePermissions } from '../../contexts/PermissionsContext';
 import { useAdminDarkMode } from '../../contexts/AdminDarkModeContext';
 import { useFeatureFlags, type FeatureKey } from '../../contexts/FeatureFlagsContext';
@@ -324,6 +326,20 @@ export const AdminSidebar: React.FC<AdminSidebarProps> = ({ isOpen, onClose, col
 
             {/* Storage Info */}
             <StorageInfo />
+
+            {/* Link to the project on GitHub (#778). Subtle footer row so
+                admins can reach the repo — star, source, report an issue —
+                from anywhere in the dashboard, not just the setup screen. */}
+            <a
+              href={repoUrl}
+              target="_blank"
+              rel="noopener noreferrer"
+              className="mx-4 mb-3 flex items-center gap-2 text-xs text-neutral-500 dark:text-neutral-400 hover:text-neutral-700 dark:hover:text-neutral-200 transition-colors"
+              title={t('admin.viewOnGithub', 'View PicPeak on GitHub')}
+            >
+              <Github className="w-3.5 h-3.5" />
+              <span>{t('admin.viewOnGithub', 'View PicPeak on GitHub')}</span>
+            </a>
           </div>
         )}
       </div>

frontend/src/i18n/locales/de.json

@@ -2411,6 +2411,7 @@
       "channelBeta": "Beta",
       "beta": "BETA",
       "viewReleaseNotes": "Versionshinweise anzeigen",
+      "viewOnGithub": "PicPeak auf GitHub ansehen",
       "updateAvailableShort": "v{{version}} verfügbar",
       "upToDate": "Alles aktuell",
       "updateNow": "Jetzt aktualisieren",

frontend/src/i18n/locales/en.json

@@ -1987,6 +1987,7 @@
       "channelBeta": "Beta",
       "beta": "BETA",
       "viewReleaseNotes": "View Release Notes",
+      "viewOnGithub": "View PicPeak on GitHub",
       "updateAvailableShort": "v{{version}} available",
       "upToDate": "You're up to date",
       "updateNow": "Update Now",

frontend/src/utils/githubReleaseUrl.ts

@@ -10,5 +10,10 @@
  * notes for the running version (#566) and by the update-available
  * indicator to link to the upgrade target's notes.
  */
+/** Repository home on GitHub. Single source of truth for the org URL so
+ *  links (release notes, the admin "view on GitHub" button, #778) don't
+ *  each hardcode it. */
+export const repoUrl = 'https://github.com/PicPeak/picpeak';
+
 export const githubReleaseUrl = (version: string): string =>
-  `https://github.com/PicPeak/picpeak/releases/tag/v${version}`;
+  `${repoUrl}/releases/tag/v${version}`;