Initial commit: scan_web integrated recording UI

FastAPI backend + vanilla JS frontend for LiDAR/camera startup, camera
settings, and rosbag recording, unifying the previous scan_gui/scan_gui_dual/
scan_gui_triple desktop tools into one web app.

backend/routers/camera.py

@@ -0,0 +1,82 @@
+from __future__ import annotations
+
+from fastapi import APIRouter, HTTPException, Request
+from fastapi.responses import StreamingResponse
+from pydantic import BaseModel
+from starlette.concurrency import run_in_threadpool
+
+import camera_params
+import config
+
+router = APIRouter(prefix="/api/camera", tags=["camera"])
+
+
+class ParamValuesIn(BaseModel):
+    exposure_auto: bool
+    exposure_auto_target_brightness: int
+    exposure_auto_min: float
+    exposure_auto_max: float
+    exposure_time: int
+    gain: float
+
+
+def _get_spec(request: Request, cam_id: str) -> config.CameraSpec:
+    session = request.app.state.session
+    specs = {c.id: c for c in config.camera_specs(session.camera_count)}
+    spec = specs.get(cam_id)
+    if spec is None:
+        raise HTTPException(404, f"unknown camera id '{cam_id}' for camera_count={session.camera_count}")
+    return spec
+
+
+@router.get("/{cam_id}/params")
+async def get_params(cam_id: str, request: Request):
+    spec = _get_spec(request, cam_id)
+    session = request.app.state.session
+    values = session.camera_values.get(cam_id) or camera_params.load_defaults(spec)
+    session.camera_values[cam_id] = values
+    return values.as_dict()
+
+
+@router.post("/{cam_id}/params")
+async def set_params(cam_id: str, body: ParamValuesIn, request: Request):
+    spec = _get_spec(request, cam_id)
+    session = request.app.state.session
+    values = camera_params.CameraParamValues(**body.model_dump())
+    session.camera_values[cam_id] = values
+    return {"ok": True}
+
+
+@router.post("/{cam_id}/params/apply")
+async def apply_params(cam_id: str, request: Request):
+    spec = _get_spec(request, cam_id)
+    session = request.app.state.session
+    pm = request.app.state.pm
+    if not pm.is_running("camera"):
+        raise HTTPException(409, "camera is not running")
+    values = session.camera_values.get(cam_id) or camera_params.load_defaults(spec)
+    results = await run_in_threadpool(camera_params.apply_params, spec, values)
+    ok = all(r["ok"] for r in results)
+    return {"ok": ok, "results": results}
+
+
+@router.post("/{cam_id}/params/save")
+async def save_params(cam_id: str, request: Request):
+    spec = _get_spec(request, cam_id)
+    session = request.app.state.session
+    values = session.camera_values.get(cam_id) or camera_params.load_defaults(spec)
+    try:
+        await run_in_threadpool(camera_params.save_params, spec, values)
+    except Exception as e:
+        raise HTTPException(500, f"save failed: {e}")
+    return {"ok": True, "path": spec.base_params_path}
+
+
+@router.get("/{cam_id}/stream.mjpg")
+async def stream(cam_id: str, request: Request):
+    _get_spec(request, cam_id)  # validate
+    ros = request.app.state.ros
+    return StreamingResponse(
+        ros.mjpeg_generator(cam_id),
+        media_type="multipart/x-mixed-replace; boundary=frame",
+    )