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>

package.json

@@ -15,6 +15,9 @@
     "@dnd-kit/utilities": "^3.2.2",
     "@ffmpeg/ffmpeg": "^0.12.15",
     "@ffmpeg/util": "^0.12.2",
+    "@fontsource-variable/inter": "^5.2.8",
+    "@fontsource-variable/plus-jakarta-sans": "^5.2.8",
+    "@fontsource/vazirmatn": "^5.2.8",
     "@hookform/resolvers": "^5.2.2",
     "@nexrender/core": "^1.46.0",
     "@radix-ui/react-accordion": "^1.2.12",