Add per-task-type submission configuration with client-side movie spec checks

Coordinators can configure, per task type, accepted file extensions, a
naming convention, and (for video files) required resolution/format/
codec/frame rate. All checking happens entirely client-side in the
browser before upload - the backend only stores and validates the
configuration itself, never inspects submitted files.

- backend: submission_config_by_task_type JSON column on Project,
  schemas/submission_config.py for validation, GET/PUT
  /projects/{id}/submission-config endpoints. Added .mxf/.ma/.usd(a/c)
  to the supported file formats.
- frontend: new Submissions tab in Project Settings
  (SubmissionConfigManager.vue) to configure rules per task type.
  TaskSubmissions.vue enforces them before upload: extension/naming
  checks via regex, and real video resolution/codec/frame rate
  detection via mediainfo.js (parses container metadata directly,
  so it works for formats browsers can't play natively like MXF,
  ProRes, or DNxHD).

backend/utils/file_handler.py

@@ -21,21 +21,23 @@ class FileHandler:
     # Supported VFX media formats
     SUPPORTED_FORMATS = {
         # Video formats
-        '.mov', '.mp4', '.avi', '.mkv', '.webm',
+        '.mov', '.mp4', '.avi', '.mkv', '.webm', '.mxf',
         # Image formats
         '.exr', '.jpg', '.jpeg', '.png', '.tiff', '.tif', '.dpx', '.hdr',
         # Document formats
         '.pdf', '.txt', '.doc', '.docx',
         # Archive formats
-        '.zip', '.rar', '.7z'
+        '.zip', '.rar', '.7z',
+        # Scene formats
+        '.ma', '.usd', '.usda', '.usdc'
     }
-    
+
     # File size limits (in bytes)
     MAX_ATTACHMENT_SIZE = 10 * 1024 * 1024  # 10MB for attachments
     MAX_SUBMISSION_SIZE = 500 * 1024 * 1024  # 500MB for submissions (fallback)
-    
+
     # Movie file extensions that should use global upload limit
-    MOVIE_EXTENSIONS = {'.mov', '.mp4', '.avi', '.mkv', '.webm'}
+    MOVIE_EXTENSIONS = {'.mov', '.mp4', '.avi', '.mkv', '.webm', '.mxf'}
     
     # Thumbnail settings
     THUMBNAIL_SIZE = (200, 200)