feat: add Eventify ID (EVT-XXXXXXXX) to User model and all APIs

- Add eventify_id CharField (unique, indexed, editable=False) to User
- Auto-generate on save() with charset excluding I/O/0/1 for clarity
- Migration 0012: add field nullable, backfill all existing users, make non-null
- Sync migration 0011 (allowed_modules) pulled from server
- Expose eventify_id in accounts/api.py, partner/api.py serializers
- Expose eventify_id in mobile_api login response (populates localStorage)

accounts/models.py

@@ -1,8 +1,18 @@
+import secrets
+
 from django.contrib.auth.models import AbstractUser
 from django.db import models
 
 from accounts.manager import UserManager
 from partner.models import Partner
+
+EVENTIFY_ID_CHARS = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'  # no I, O, 0, 1
+
+
+def generate_eventify_id():
+    return 'EVT-' + ''.join(secrets.choice(EVENTIFY_ID_CHARS) for _ in range(8))
+
+
 ROLE_CHOICES = (
         ('admin', 'Admin'),
         ('manager', 'Manager'),
@@ -15,6 +25,15 @@ ROLE_CHOICES = (
     )
 
 class User(AbstractUser):
+    eventify_id = models.CharField(
+        max_length=12,
+        unique=True,
+        editable=False,
+        db_index=True,
+        null=True,
+        blank=True,
+    )
+
     phone_number = models.CharField(max_length=15, blank=True, null=True)
     role = models.CharField(max_length=20, choices=ROLE_CHOICES, default='Staff')
 
@@ -39,7 +58,7 @@ class User(AbstractUser):
 
     allowed_modules = models.TextField(
         blank=True, null=True,
-        help_text="Comma-separated module slugs this user can access"
+        help_text='Comma-separated module slugs this user can access',
     )
 
     ALL_MODULES = ["dashboard", "partners", "events", "ad-control", "users", "reviews", "contributions", "financials", "settings"]
@@ -56,5 +75,14 @@ class User(AbstractUser):
 
     objects = UserManager()
 
+    def save(self, *args, **kwargs):
+        if not self.eventify_id:
+            for _ in range(10):
+                candidate = generate_eventify_id()
+                if not User.objects.filter(eventify_id=candidate).exists():
+                    self.eventify_id = candidate
+                    break
+        super().save(*args, **kwargs)
+
     def __str__(self):
         return self.username