feat: V2 microservices stack — backend services, gateway, JWT auth

Add full V2 architecture: identity, content, studio (.NET 10) and file,
render, notification, gateway (Go) services with vendored deps, plus DB
migrations, event/API contracts, and an init-db script.

Wire the Next.js frontend to the gateway: server-side JWT auth routes
(login/register/refresh/logout/me), gateway fetch helper, and session/
cookie/jwt helpers under src/lib.

Containerize the stack via docker-compose.v2.yml and per-service
Dockerfiles. Base images resolve through a Nexus mirror (Docker Hub) and
MCR directly; npm/NuGet pull from Nexus groups. Self-host fonts via
next/font/local to avoid Google Fonts (geo-blocked).

Add CI workflow and ignore .env.v2, *.stackdump, and .NET bin/obj.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

services/file/docker-compose.yml

@@ -0,0 +1,32 @@
+version: "3.9"
+
+services:
+  minio:
+    image: minio/minio:latest
+    command: server /data --console-address ":9001"
+    environment:
+      MINIO_ROOT_USER: minioadmin
+      MINIO_ROOT_PASSWORD: minioadmin
+    ports:
+      - "9000:9000"
+      - "9001:9001"
+    volumes:
+      - minio_data:/data
+
+  file-svc:
+    build: .
+    ports:
+      - "5012:8080"
+    environment:
+      DATABASE_URL: "postgresql://postgres:postgres@postgres:5432/flatrender?search_path=file_mgr,public"
+      JWT_SECRET: "dev-secret-32-chars-minimum-here!!"
+      MINIO_ENDPOINT: "minio:9000"
+      MINIO_ACCESS_KEY: "minioadmin"
+      MINIO_SECRET_KEY: "minioadmin"
+      MINIO_UPLOAD_BUCKET: "user-uploads"
+      GIN_MODE: "debug"
+    depends_on:
+      - minio
+
+volumes:
+  minio_data: