feat(backend): add ontology and orchestrator API endpoints

New endpoints:
- server/src/app/api/v1/endpoints/ontology.py: ontology API
- server/src/app/api/v1/endpoints/orchestrator.py: orchestrator API

New schemas:
- server/src/app/schemas/ontology.py: ontology data schemas
- server/src/app/schemas/orchestrator.py: orchestrator data schemas
- server/src/app/schemas/user_agent.py: user agent data schemas

New services:
- server/src/app/services/ontology.py: ontology business logic
- server/src/app/services/orchestrator.py: orchestrator business logic
- server/src/app/services/runtime_chat.py: runtime chat service
- server/src/app/services/user_agent.py: user agent service

New tests:
- server/tests/test_ontology_service.py
- server/tests/test_orchestrator_service.py
- server/tests/test_user_agent_service.py

server/src/app/api/v1/endpoints/ontology.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_db
+from app.schemas.common import ErrorResponse
+from app.schemas.ontology import OntologyParseRequest, OntologyParseResult
+from app.services.ontology import SemanticOntologyService
+
+router = APIRouter(prefix="/ontology")
+DbSession = Annotated[Session, Depends(get_db)]
+
+
+@router.post(
+    "/parse",
+    response_model=OntologyParseResult,
+    summary="解析自然语言为语义本体",
+    description=(
+        "把自然语言问题解析成 Day 3 约定的 8 个核心字段，"
+        "并写入 AgentRun 与 SemanticParseLog。"
+    ),
+    responses={
+        status.HTTP_400_BAD_REQUEST: {
+            "model": ErrorResponse,
+            "description": "请求缺少有效 query 或解析请求格式不合法。",
+        }
+    },
+)
+def parse_ontology(payload: OntologyParseRequest, db: DbSession) -> OntologyParseResult:
+    try:
+        return SemanticOntologyService(db).parse(payload)
+    except ValueError as exc:
+        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(exc)) from exc

server/src/app/api/v1/endpoints/orchestrator.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_db
+from app.schemas.common import ErrorResponse
+from app.schemas.orchestrator import OrchestratorRequest, OrchestratorResponse
+from app.services.orchestrator import OrchestratorService
+
+router = APIRouter(prefix="/orchestrator")
+DbSession = Annotated[Session, Depends(get_db)]
+
+
+@router.post(
+    "/run",
+    response_model=OrchestratorResponse,
+    summary="运行 Orchestrator 统一调度",
+    description="统一接收用户消息、定时任务和系统事件，完成语义解析、权限判断、路由和占位执行。",
+    responses={
+        status.HTTP_400_BAD_REQUEST: {
+            "model": ErrorResponse,
+            "description": "请求缺少 message 或 task_id，无法启动调度。",
+        }
+    },
+)
+def run_orchestrator(payload: OrchestratorRequest, db: DbSession) -> OrchestratorResponse:
+    try:
+        return OrchestratorService(db).run(payload)
+    except ValueError as exc:
+        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(exc)) from exc