feat: git SHA version badge in admin, fix finanzplan caching, drop gitea remote

- AdminShell: shows NEXT_PUBLIC_GIT_SHA in sidebar footer
- Dockerfile + build-pitch-deck.yml: pass --build-arg GIT_SHA at build time
- FinanzplanSlide: fetch with cache:no-store to always show current DB values
- finanzplan routes: Cache-Control: no-store to prevent CDN/proxy staling
- CLAUDE.md: remove dead gitea remote (only origin exists)

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

pitch-deck/components/pitch-admin/AdminShell.tsx

@@ -92,6 +92,11 @@ export default function AdminShell({ admin, children }: AdminShellProps) {
             <div className="px-3 py-2 mb-2">
               <div className="text-sm font-medium text-white/90 truncate">{admin.name}</div>
               <div className="text-xs text-white/40 truncate">{admin.email}</div>
+              <div className="mt-1.5 flex items-center gap-1.5">
+                <span className="text-[9px] font-mono bg-white/[0.06] text-white/30 px-1.5 py-0.5 rounded">
+                  {process.env.NEXT_PUBLIC_GIT_SHA ?? 'dev'}
+                </span>
+              </div>
             </div>
             <button
               onClick={logout}