fix: GPS缺失下的数据缺失问题

backend/monitoring/video.py

@@ -103,13 +103,17 @@ class VideoDisplayProbeStore:
 @dataclass(frozen=True)
 class FrameTrailerMetadata:
     timestamp_ns: int
-    latitude: float
-    longitude: float
+    latitude: float | None
+    longitude: float | None
     capture_to_send_ms: int
     raw_latitude_hex: str
     raw_longitude_hex: str
     received_at: float
 
+    @property
+    def has_gps_fix(self) -> bool:
+        return self.latitude is not None and self.longitude is not None
+
 
 @dataclass(frozen=True)
 class VideoDisplayProbeStatus:
@@ -271,21 +275,23 @@ class OmniSocketVideoReceiver:
 
         if timestamp_ms <= 0:
             return None
-        if not math.isfinite(latitude) or not math.isfinite(longitude):
-            return None
-        if not (-90.0 <= latitude <= 90.0) or not (-180.0 <= longitude <= 180.0):
-            return None
-        if abs(latitude) < 1e-9 and abs(longitude) < 1e-9:
-            return None
 
         timestamp_ns = timestamp_ms * VIDEO_TRAILER_TIMESTAMP_MULTIPLIER_NS
         if abs(time.time_ns() - timestamp_ns) > VIDEO_TRAILER_TIMESTAMP_MAX_SKEW_NS:
             return None
 
+        gps_fix_available = (
+            math.isfinite(latitude)
+            and math.isfinite(longitude)
+            and (-90.0 <= latitude <= 90.0)
+            and (-180.0 <= longitude <= 180.0)
+            and not (abs(latitude) < 1e-9 and abs(longitude) < 1e-9)
+        )
+
         return FrameTrailerMetadata(
             timestamp_ns=timestamp_ns,
-            latitude=latitude,
-            longitude=longitude,
+            latitude=latitude if gps_fix_available else None,
+            longitude=longitude if gps_fix_available else None,
             capture_to_send_ms=int(capture_to_send_ms),
             raw_latitude_hex=trailer[8:16].hex(),
             raw_longitude_hex=trailer[16:24].hex(),