refactor(gateway): restructure gateway with new dependency injection and services

Reorganize app/gateway/ with:
- common/ - lifespan management
- dependencies/ - FastAPI dependency injection (db, checkpointer, repositories, stream_bridge)
- services/runs/ - run execution services (facade_factory, input adapters, store operations)
- registrar.py - router registration
- router.py - main router setup

Simplify app.py to use the new modular structure.
Remove deprecated utils.py.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/gateway/services/runs/input/request_adapter.py

@@ -0,0 +1,127 @@
+"""App-owned request adapter for runs entrypoints."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from deerflow.runtime.stream_bridge import JSONValue
+from deerflow.runtime.runs.types import RunIntent
+
+type RequestBody = dict[str, JSONValue]
+type RequestQuery = dict[str, str]
+
+
+@dataclass(frozen=True)
+class AdaptedRunRequest:
+    """
+    统一的内部请求 DTO.
+
+    路由层只负责提取 path/query/body，适配器负责转成稳定内部结构。
+    """
+
+    intent: RunIntent
+    thread_id: str | None
+    run_id: str | None
+    body: RequestBody
+    headers: dict[str, str]
+    query: RequestQuery
+
+    @property
+    def last_event_id(self) -> str | None:
+        """Extract Last-Event-ID from headers."""
+        return self.headers.get("last-event-id") or self.headers.get("Last-Event-ID")
+
+    @property
+    def is_stateless(self) -> bool:
+        """Check if this is a stateless request."""
+        return self.thread_id is None
+
+
+def adapt_create_run_request(
+    *,
+    thread_id: str | None,
+    body: RequestBody,
+    headers: dict[str, str] | None = None,
+    query: RequestQuery | None = None,
+) -> AdaptedRunRequest:
+    """Adapt POST /threads/{thread_id}/runs or POST /runs."""
+    return AdaptedRunRequest(
+        intent="create_background",
+        thread_id=thread_id,
+        run_id=None,
+        body=body,
+        headers=headers or {},
+        query=query or {},
+    )
+
+
+def adapt_create_stream_request(
+    *,
+    thread_id: str | None,
+    body: RequestBody,
+    headers: dict[str, str] | None = None,
+    query: RequestQuery | None = None,
+) -> AdaptedRunRequest:
+    """Adapt POST /threads/{thread_id}/runs/stream or POST /runs/stream."""
+    return AdaptedRunRequest(
+        intent="create_and_stream",
+        thread_id=thread_id,
+        run_id=None,
+        body=body,
+        headers=headers or {},
+        query=query or {},
+    )
+
+
+def adapt_create_wait_request(
+    *,
+    thread_id: str | None,
+    body: RequestBody,
+    headers: dict[str, str] | None = None,
+    query: RequestQuery | None = None,
+) -> AdaptedRunRequest:
+    """Adapt POST /threads/{thread_id}/runs/wait or POST /runs/wait."""
+    return AdaptedRunRequest(
+        intent="create_and_wait",
+        thread_id=thread_id,
+        run_id=None,
+        body=body,
+        headers=headers or {},
+        query=query or {},
+    )
+
+
+def adapt_join_stream_request(
+    *,
+    thread_id: str,
+    run_id: str,
+    headers: dict[str, str] | None = None,
+    query: RequestQuery | None = None,
+) -> AdaptedRunRequest:
+    """Adapt GET /threads/{thread_id}/runs/{run_id}/stream."""
+    return AdaptedRunRequest(
+        intent="join_stream",
+        thread_id=thread_id,
+        run_id=run_id,
+        body={},
+        headers=headers or {},
+        query=query or {},
+    )
+
+
+def adapt_join_wait_request(
+    *,
+    thread_id: str,
+    run_id: str,
+    headers: dict[str, str] | None = None,
+    query: RequestQuery | None = None,
+) -> AdaptedRunRequest:
+    """Adapt GET /threads/{thread_id}/runs/{run_id}/join."""
+    return AdaptedRunRequest(
+        intent="join_wait",
+        thread_id=thread_id,
+        run_id=run_id,
+        body={},
+        headers=headers or {},
+        query=query or {},
+    )