fix(web): Caddyfile ins Image backen — SPA statt Caddy-Default-Seite

Das web-Runtime-Image (caddy:2-alpine) hatte keine eigene Config, daher
lieferte Caddy seine Default-Welcome-Seite aus /usr/share/caddy statt der
gebauten SPA aus /srv ("Caddy works!"). Eigene Caddyfile (root /srv,
try_files SPA-Fallback) wird jetzt nach /etc/caddy/Caddyfile kopiert.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/Dockerfile

@@ -19,6 +19,8 @@ COPY packages/shared ./packages/shared
 
 RUN pnpm --filter web build
 
-# --- runtime (static via Caddy in production compose) ---
+# --- runtime (static via Caddy) ---
 FROM caddy:2-alpine AS runtime
+# Eigene Caddy-Config statt der Default-Welcome-Seite: SPA aus /srv ausliefern.
+COPY apps/web/Caddyfile /etc/caddy/Caddyfile
 COPY --from=builder /repo/apps/web/dist /srv