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/render/vendor/github.com/goccy/go-json/query.go

@@ -0,0 +1,47 @@
+package json
+
+import (
+	"github.com/goccy/go-json/internal/encoder"
+)
+
+type (
+	// FieldQuery you can dynamically filter the fields in the structure by creating a FieldQuery,
+	// adding it to context.Context using SetFieldQueryToContext and then passing it to MarshalContext.
+	// This is a type-safe operation, so it is faster than filtering using map[string]interface{}.
+	FieldQuery       = encoder.FieldQuery
+	FieldQueryString = encoder.FieldQueryString
+)
+
+var (
+	// FieldQueryFromContext get current FieldQuery from context.Context.
+	FieldQueryFromContext = encoder.FieldQueryFromContext
+	// SetFieldQueryToContext set current FieldQuery to context.Context.
+	SetFieldQueryToContext = encoder.SetFieldQueryToContext
+)
+
+// BuildFieldQuery builds FieldQuery by fieldName or sub field query.
+// First, specify the field name that you want to keep in structure type.
+// If the field you want to keep is a structure type, by creating a sub field query using BuildSubFieldQuery,
+// you can select the fields you want to keep in the structure.
+// This description can be written recursively.
+func BuildFieldQuery(fields ...FieldQueryString) (*FieldQuery, error) {
+	query, err := Marshal(fields)
+	if err != nil {
+		return nil, err
+	}
+	return FieldQueryString(query).Build()
+}
+
+// BuildSubFieldQuery builds sub field query.
+func BuildSubFieldQuery(name string) *SubFieldQuery {
+	return &SubFieldQuery{name: name}
+}
+
+type SubFieldQuery struct {
+	name string
+}
+
+func (q *SubFieldQuery) Fields(fields ...FieldQueryString) FieldQueryString {
+	query, _ := Marshal(map[string][]FieldQueryString{q.name: fields})
+	return FieldQueryString(query)
+}