Grant mobile plans from verified App Store and Play purchases (#78).

The app confirms a StoreKit signed transaction or Play purchase token. The backend checks it with Apple or Google before writing the ledger, and the RevenueCat webhook no longer grants access.

llm_be/monetization/migrations/0006_store_purchase_sources.py

@@ -0,0 +1,56 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("finance", "0005_revenuecat_fields"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="invoice",
+            name="provider",
+            field=models.CharField(
+                choices=[
+                    ("stripe", "Stripe"),
+                    ("revenuecat", "RevenueCat"),
+                    ("app_store", "App Store"),
+                    ("play_store", "Play Store"),
+                ],
+                default="stripe",
+                max_length=32,
+            ),
+        ),
+        migrations.AlterField(
+            model_name="payment",
+            name="provider",
+            field=models.CharField(
+                choices=[
+                    ("stripe", "Stripe"),
+                    ("revenuecat", "RevenueCat"),
+                    ("app_store", "App Store"),
+                    ("play_store", "Play Store"),
+                ],
+                default="stripe",
+                max_length=32,
+            ),
+        ),
+        migrations.AlterField(
+            model_name="usersubscription",
+            name="source",
+            field=models.CharField(
+                choices=[
+                    ("none", "None"),
+                    ("stripe", "Stripe"),
+                    ("revenuecat", "RevenueCat"),
+                    ("app_store", "App Store"),
+                    ("play_store", "Play Store"),
+                    ("backer", "Backer"),
+                    ("admin", "Admin"),
+                ],
+                default="none",
+                max_length=32,
+            ),
+        ),
+    ]