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/models/project.py

@@ -53,7 +53,10 @@ class Project(Base):
     
     # Custom task statuses
     custom_task_statuses = Column(JSON, nullable=True)  # Custom task statuses for project
-    
+
+    # Submission configuration per task type
+    submission_config_by_task_type = Column(JSON, nullable=True)  # Allowed file types, naming pattern, required flag per task type
+
     # Project thumbnail
     thumbnail_path = Column(String, nullable=True)  # Path to project thumbnail image