feat(content): graphql subgraph with dataloader for textbook/chapter/kp/question

- GraphQLModule: Apollo Federation 2 at /graphql

- Textbook/Chapter/KnowledgePoint/Question @key with @ResolveReference

- RouterAuthGuard: validate Router-Authorization header (ADR-036)

- batchFind methods added to 4 repositories

- Domain modules export repositories for GraphqlModule injection

services/content/package.json

@@ -12,10 +12,14 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
+    "@apollo/subgraph": "^2.2.3",
+    "@edu/shared-ts": "workspace:*",
     "@grpc/grpc-js": "^1.12.0",
     "@grpc/proto-loader": "^0.7.13",
+    "@nestjs/apollo": "^12.2.0",
     "@nestjs/common": "^10.4.0",
     "@nestjs/core": "^10.4.0",
+    "@nestjs/graphql": "^12.2.0",
     "@nestjs/microservices": "^10.4.0",
     "@nestjs/platform-express": "^10.4.0",
     "@opentelemetry/api": "^1.9.0",
@@ -24,7 +28,9 @@
     "@opentelemetry/sdk-node": "^0.55.0",
     "@elastic/elasticsearch": "^8.13.0",
     "@paralleldrive/cuid2": "^2.2.2",
+    "dataloader": "^2.2.2",
     "drizzle-orm": "^0.31.0",
+    "graphql": "^16.9.0",
     "kafkajs": "^2.2.4",
     "mysql2": "^3.11.0",
     "neo4j-driver": "^5.23.0",