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/vendor/github.com/goccy/go-json/path.go

@@ -0,0 +1,84 @@
+package json
+
+import (
+	"reflect"
+
+	"github.com/goccy/go-json/internal/decoder"
+)
+
+// CreatePath creates JSON Path.
+//
+// JSON Path rule
+// $   : root object or element. The JSON Path format must start with this operator, which refers to the outermost level of the JSON-formatted string.
+// .   : child operator. You can identify child values using dot-notation.
+// ..  : recursive descent.
+// []  : subscript operator. If the JSON object is an array, you can use brackets to specify the array index.
+// [*] : all objects/elements for array.
+//
+// Reserved words must be properly escaped when included in Path.
+//
+// Escape Rule
+// single quote style escape: e.g.) `$['a.b'].c`
+// double quote style escape: e.g.) `$."a.b".c`
+func CreatePath(p string) (*Path, error) {
+	path, err := decoder.PathString(p).Build()
+	if err != nil {
+		return nil, err
+	}
+	return &Path{path: path}, nil
+}
+
+// Path represents JSON Path.
+type Path struct {
+	path *decoder.Path
+}
+
+// RootSelectorOnly whether only the root selector ($) is used.
+func (p *Path) RootSelectorOnly() bool {
+	return p.path.RootSelectorOnly
+}
+
+// UsedSingleQuotePathSelector whether single quote-based escaping was done when building the JSON Path.
+func (p *Path) UsedSingleQuotePathSelector() bool {
+	return p.path.SingleQuotePathSelector
+}
+
+// UsedSingleQuotePathSelector whether double quote-based escaping was done when building the JSON Path.
+func (p *Path) UsedDoubleQuotePathSelector() bool {
+	return p.path.DoubleQuotePathSelector
+}
+
+// Extract extracts a specific JSON string.
+func (p *Path) Extract(data []byte, optFuncs ...DecodeOptionFunc) ([][]byte, error) {
+	return extractFromPath(p, data, optFuncs...)
+}
+
+// PathString returns original JSON Path string.
+func (p *Path) PathString() string {
+	return p.path.String()
+}
+
+// Unmarshal extract and decode the value of the part corresponding to JSON Path from the input data.
+func (p *Path) Unmarshal(data []byte, v interface{}, optFuncs ...DecodeOptionFunc) error {
+	contents, err := extractFromPath(p, data, optFuncs...)
+	if err != nil {
+		return err
+	}
+	results := make([]interface{}, 0, len(contents))
+	for _, content := range contents {
+		var result interface{}
+		if err := Unmarshal(content, &result); err != nil {
+			return err
+		}
+		results = append(results, result)
+	}
+	if err := decoder.AssignValue(reflect.ValueOf(results), reflect.ValueOf(v)); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Get extract and substitute the value of the part corresponding to JSON Path from the input value.
+func (p *Path) Get(src, dst interface{}) error {
+	return p.path.Get(reflect.ValueOf(src), reflect.ValueOf(dst))
+}