Fix model-controller mismatches and routing issues

- ticket: add user_id, priority, category fields; fix _serialize_ticket -> _serialize
- package: fix is_active -> active (Odoo auto-filter), remove invalid entity_id filter
- walkthrough: add sequence field; fix controller to use name/content instead of title/steps
- users: fix encoach_user_type -> encoach_type, encoach_entity_id -> entity_rel_ids.entity_id
- generation: use EncoachGenerationService class instead of nonexistent ORM model,
  fix /api/exam/level/ route conflict (separate GET and POST URLs)

Made-with: Cursor

encoach_training/models/walkthrough.py

@@ -6,6 +6,7 @@ class EncoachWalkthrough(models.Model):
     _description = "EnCoach Walkthrough"
 
     name = fields.Char()
+    sequence = fields.Integer(default=10)
     content = fields.Json()
     module = fields.Selection(
         [