fix: add missing deviceEnvInfo for video generation payload

The Grok API requires deviceEnvInfo field to correctly parse resolutionName.
Without this field, the backend ignores resolution settings and generates
low-resolution videos regardless of the requested quality.

Added deviceEnvInfo with standard 1920x1080 viewport settings to ensure
720p and other resolution settings are properly respected by the API.

Tested: 720p videos now correctly generate at 720x1280 resolution.

app/services/grok/services/media.py

@@ -158,6 +158,14 @@ class VideoService:
             "message": f"{prompt} {mode_flag}",
             "toolOverrides": {"videoGen": True},
             "enableSideBySide": True,
+            "deviceEnvInfo": {
+                "darkModeEnabled": False,
+                "devicePixelRatio": 2,
+                "screenWidth": 1920,
+                "screenHeight": 1080,
+                "viewportWidth": 1920,
+                "viewportHeight": 1080,
+            },
             "responseMetadata": {
                 "experiments": [],
                 "modelConfigOverride": {