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/notification/vendor/github.com/gin-gonic/gin/internal/bytesconv/bytesconv_1.19.go

@@ -0,0 +1,26 @@
+// Copyright 2020 Gin Core Team. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.20
+
+package bytesconv
+
+import (
+	"unsafe"
+)
+
+// StringToBytes converts string to byte slice without a memory allocation.
+func StringToBytes(s string) []byte {
+	return *(*[]byte)(unsafe.Pointer(
+		&struct {
+			string
+			Cap int
+		}{s, len(s)},
+	))
+}
+
+// BytesToString converts byte slice to string without a memory allocation.
+func BytesToString(b []byte) string {
+	return *(*string)(unsafe.Pointer(&b))
+}

services/notification/vendor/github.com/gin-gonic/gin/internal/bytesconv/bytesconv_1.20.go

@@ -0,0 +1,23 @@
+// Copyright 2023 Gin Core Team. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+//go:build go1.20
+
+package bytesconv
+
+import (
+	"unsafe"
+)
+
+// StringToBytes converts string to byte slice without a memory allocation.
+// For more details, see https://github.com/golang/go/issues/53003#issuecomment-1140276077.
+func StringToBytes(s string) []byte {
+	return unsafe.Slice(unsafe.StringData(s), len(s))
+}
+
+// BytesToString converts byte slice to string without a memory allocation.
+// For more details, see https://github.com/golang/go/issues/53003#issuecomment-1140276077.
+func BytesToString(b []byte) string {
+	return unsafe.String(unsafe.SliceData(b), len(b))
+}

services/notification/vendor/github.com/gin-gonic/gin/internal/json/go_json.go

@@ -0,0 +1,22 @@
+// Copyright 2017 Bo-Yi Wu. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+//go:build go_json
+
+package json
+
+import json "github.com/goccy/go-json"
+
+var (
+	// Marshal is exported by gin/json package.
+	Marshal = json.Marshal
+	// Unmarshal is exported by gin/json package.
+	Unmarshal = json.Unmarshal
+	// MarshalIndent is exported by gin/json package.
+	MarshalIndent = json.MarshalIndent
+	// NewDecoder is exported by gin/json package.
+	NewDecoder = json.NewDecoder
+	// NewEncoder is exported by gin/json package.
+	NewEncoder = json.NewEncoder
+)

services/notification/vendor/github.com/gin-gonic/gin/internal/json/json.go

@@ -0,0 +1,22 @@
+// Copyright 2017 Bo-Yi Wu. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+//go:build !jsoniter && !go_json && !(sonic && avx && (linux || windows || darwin) && amd64)
+
+package json
+
+import "encoding/json"
+
+var (
+	// Marshal is exported by gin/json package.
+	Marshal = json.Marshal
+	// Unmarshal is exported by gin/json package.
+	Unmarshal = json.Unmarshal
+	// MarshalIndent is exported by gin/json package.
+	MarshalIndent = json.MarshalIndent
+	// NewDecoder is exported by gin/json package.
+	NewDecoder = json.NewDecoder
+	// NewEncoder is exported by gin/json package.
+	NewEncoder = json.NewEncoder
+)

services/notification/vendor/github.com/gin-gonic/gin/internal/json/jsoniter.go

@@ -0,0 +1,23 @@
+// Copyright 2017 Bo-Yi Wu. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+//go:build jsoniter
+
+package json
+
+import jsoniter "github.com/json-iterator/go"
+
+var (
+	json = jsoniter.ConfigCompatibleWithStandardLibrary
+	// Marshal is exported by gin/json package.
+	Marshal = json.Marshal
+	// Unmarshal is exported by gin/json package.
+	Unmarshal = json.Unmarshal
+	// MarshalIndent is exported by gin/json package.
+	MarshalIndent = json.MarshalIndent
+	// NewDecoder is exported by gin/json package.
+	NewDecoder = json.NewDecoder
+	// NewEncoder is exported by gin/json package.
+	NewEncoder = json.NewEncoder
+)

services/notification/vendor/github.com/gin-gonic/gin/internal/json/sonic.go

@@ -0,0 +1,23 @@
+// Copyright 2022 Gin Core Team. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+//go:build sonic && avx && (linux || windows || darwin) && amd64
+
+package json
+
+import "github.com/bytedance/sonic"
+
+var (
+	json = sonic.ConfigStd
+	// Marshal is exported by gin/json package.
+	Marshal = json.Marshal
+	// Unmarshal is exported by gin/json package.
+	Unmarshal = json.Unmarshal
+	// MarshalIndent is exported by gin/json package.
+	MarshalIndent = json.MarshalIndent
+	// NewDecoder is exported by gin/json package.
+	NewDecoder = json.NewDecoder
+	// NewEncoder is exported by gin/json package.
+	NewEncoder = json.NewEncoder
+)