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/Dockerfile

@@ -12,6 +12,10 @@ RUN npm install
 # Copy source code
 COPY . .
 
+# Embed git commit hash into build
+ARG GIT_SHA=dev
+ENV GIT_SHA=$GIT_SHA
+
 # Build the application
 RUN npm run build