feat(ai): v2 新增 GenerateReport RPC + ReportService

第 9 个 RPC GenerateReport（学情报告生成）：data-ana 学情数据 → LLM 生成 → 结构化提取

新增 ReportService 业务编排层 + GenerateReportRequest/GeneratedReport 模型

gRPC servicer + HTTP POST /v1/ai/generate/report（权限 ai:report:generate）

proto_gen 重新生成 + 测试覆盖（servicer/service/HTTP/模型/权限 共 26 用例）

402 测试通过，覆盖率 88.5%

services/ai/tests/test_models.py

@@ -6,6 +6,10 @@ from pydantic import ValidationError
 from src.ai.models.chat import ChatData, ChatMessage, ChatRequest, Usage
 from src.ai.models.expression import OptimizeExpressionRequest
 from src.ai.models.question import GeneratedQuestionData, GenerateQuestionRequest
+from src.ai.models.report import (
+    GeneratedReportData,
+    GenerateReportRequest,
+)
 from src.ai.models.workflow import (
     ConfirmRequest,
     LessonPreparationRequest,
@@ -52,8 +56,11 @@ class TestChatModels:
 
     def test_chat_data_degraded_fields(self) -> None:
         data = ChatData(
-            content="x", model="m", usage=Usage(),
-            degraded=True, degraded_reason="test",
+            content="x",
+            model="m",
+            usage=Usage(),
+            degraded=True,
+            degraded_reason="test",
         )
         assert data.degraded is True
 
@@ -131,3 +138,37 @@ class TestWorkflowModels:
         assert data.questions == []
         assert data.error is None
         assert data.degraded is False
+
+
+class TestReportModels:
+    """学情报告模型测试."""
+
+    def test_generate_report_request_defaults(self) -> None:
+        req = GenerateReportRequest(class_id="c-1")
+        assert req.report_type == "class_summary"
+        assert req.student_id is None
+        assert req.user_id is None
+        assert req.data_scope is None
+
+    def test_generate_report_request_invalid_type(self) -> None:
+        with pytest.raises(ValidationError):
+            GenerateReportRequest(class_id="c-1", report_type="invalid")
+
+    def test_generate_report_request_missing_class_id(self) -> None:
+        with pytest.raises(ValidationError):
+            GenerateReportRequest()
+
+    def test_generate_report_request_student_detail(self) -> None:
+        req = GenerateReportRequest(
+            class_id="c-1",
+            report_type="student_detail",
+            student_id="s-001",
+        )
+        assert req.report_type == "student_detail"
+        assert req.student_id == "s-001"
+
+    def test_generated_report_data_defaults(self) -> None:
+        data = GeneratedReportData(id="r-1", content="内容", summary="摘要")
+        assert data.recommendations == []
+        assert data.degraded is False
+        assert data.degraded_reason == ""