Bump CACHEBUST to v8 for backend and frontend rebuilds; update Nginx and NostrAuthGuard to handle X-Forwarded-Prefix for NIP-98 compliance

docker-compose.yml

@@ -20,7 +20,7 @@ services:
       context: .
       dockerfile: Dockerfile
       args:
-        CACHEBUST: "7"
+        CACHEBUST: "8"
         VITE_USE_MOCK_DATA: "false"
         VITE_CONTENT_ORIGIN: ${FRONTEND_URL}
         VITE_INDEEHUB_API_URL: /api
@@ -47,7 +47,7 @@ services:
       context: ./backend
       dockerfile: Dockerfile
       args:
-        CACHEBUST: "7"
+        CACHEBUST: "8"
     restart: unless-stopped
     environment:
       # ── Core ─────────────────────────────────────────────
@@ -179,7 +179,7 @@ services:
       context: ./backend
       dockerfile: Dockerfile.ffmpeg
       args:
-        CACHEBUST: "7"
+        CACHEBUST: "8"
     restart: unless-stopped
     environment:
       ENVIRONMENT: production