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/slides/FinanzplanSlide.tsx

@@ -84,7 +84,7 @@ export default function FinanzplanSlide({ lang, investorId, preferredScenarioId
 
   // Load sheet list
   useEffect(() => {
-    fetch('/api/finanzplan')
+    fetch('/api/finanzplan', { cache: 'no-store' })
       .then(r => r.json())
       .then(data => setSheets(data.sheets || []))
       .catch(() => {})
@@ -99,7 +99,7 @@ export default function FinanzplanSlide({ lang, investorId, preferredScenarioId
     }
     setLoading(true)
     try {
-      const r = await fetch(`/api/finanzplan/${name}${fpScenarioParam}`)
+      const r = await fetch(`/api/finanzplan/${name}${fpScenarioParam}`, { cache: 'no-store' })
       const data = await r.json()
       setRows(data.rows || [])
     } catch { /* ignore */ }