feat: module-driven onboarding system + simplified 3-step signup

Add OnboardingProviderProtocol so modules declare their own post-signup
onboarding steps. The core OnboardingAggregator discovers enabled
providers and exposes a dashboard API (GET /dashboard/onboarding).
A session-scoped banner on the store dashboard shows a checklist that
guides merchants through setup without blocking signup.

Signup is simplified from 4 steps to 3 (Plan → Account → Payment):
store creation is merged into account creation, store language is
captured from the user's browsing language, and platform-specific
template branching is removed.

Includes 47 unit and integration tests covering all new providers,
the aggregator, the API endpoint, and the signup service changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/loyalty/tests/unit/test_loyalty_onboarding.py

@@ -0,0 +1,125 @@
+# app/modules/loyalty/tests/unit/test_loyalty_onboarding.py
+"""Unit tests for LoyaltyOnboardingProvider."""
+
+import uuid
+
+import pytest
+
+from app.modules.loyalty.models.loyalty_program import LoyaltyProgram, LoyaltyType
+from app.modules.loyalty.services.loyalty_onboarding import LoyaltyOnboardingProvider
+from app.modules.tenancy.models import Merchant, Store, User
+
+
+@pytest.fixture
+def loy_owner(db):
+    """Create a store owner for loyalty onboarding tests."""
+    from middleware.auth import AuthManager
+
+    auth = AuthManager()
+    user = User(
+        email=f"loyonb_{uuid.uuid4().hex[:8]}@test.com",
+        username=f"loyonb_{uuid.uuid4().hex[:8]}",
+        hashed_password=auth.hash_password("pass123"),
+        role="merchant_owner",
+        is_active=True,
+    )
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+    return user
+
+
+@pytest.fixture
+def loy_merchant(db, loy_owner):
+    """Create a merchant for loyalty onboarding tests."""
+    merchant = Merchant(
+        name="Loyalty Onboarding Merchant",
+        owner_user_id=loy_owner.id,
+        contact_email=loy_owner.email,
+        is_active=True,
+        is_verified=True,
+    )
+    db.add(merchant)
+    db.commit()
+    db.refresh(merchant)
+    return merchant
+
+
+@pytest.fixture
+def loy_store(db, loy_merchant):
+    """Create a store (no loyalty program) for loyalty onboarding tests."""
+    uid = uuid.uuid4().hex[:8]
+    store = Store(
+        merchant_id=loy_merchant.id,
+        store_code=f"LOYONB_{uid.upper()}",
+        subdomain=f"loyonb{uid.lower()}",
+        name="Loyalty Onboarding Store",
+        is_active=True,
+        is_verified=True,
+    )
+    db.add(store)
+    db.commit()
+    db.refresh(store)
+    return store
+
+
+@pytest.mark.unit
+@pytest.mark.loyalty
+class TestLoyaltyOnboardingProvider:
+    """Tests for LoyaltyOnboardingProvider."""
+
+    def setup_method(self):
+        self.provider = LoyaltyOnboardingProvider()
+
+    def test_category(self):
+        """Returns 'loyalty' as the onboarding category."""
+        assert self.provider.onboarding_category == "loyalty"
+
+    def test_get_onboarding_steps_returns_one_step(self):
+        """Returns exactly one step: create_program."""
+        steps = self.provider.get_onboarding_steps()
+        assert len(steps) == 1
+        assert steps[0].key == "loyalty.create_program"
+        assert steps[0].order == 300
+
+    def test_incomplete_without_program(self, db, loy_store):
+        """Step is incomplete when merchant has no loyalty programs."""
+        result = self.provider.is_step_completed(
+            db, loy_store.id, "loyalty.create_program"
+        )
+        assert result is False
+
+    def test_complete_with_program(self, db, loy_store, loy_merchant):
+        """Step is complete when merchant has at least one loyalty program."""
+        program = LoyaltyProgram(
+            merchant_id=loy_merchant.id,
+            loyalty_type=LoyaltyType.STAMPS.value,
+            stamps_target=10,
+            cooldown_minutes=0,
+            max_daily_stamps=10,
+            require_staff_pin=False,
+            card_name="Test Card",
+            card_color="#FF0000",
+            is_active=True,
+        )
+        db.add(program)
+        db.commit()
+
+        result = self.provider.is_step_completed(
+            db, loy_store.id, "loyalty.create_program"
+        )
+        assert result is True
+
+    def test_nonexistent_store_returns_false(self, db):
+        """Returns False for a store ID that doesn't exist."""
+        result = self.provider.is_step_completed(
+            db, 999999, "loyalty.create_program"
+        )
+        assert result is False
+
+    def test_unknown_step_key_returns_false(self, db, loy_store):
+        """Returns False for an unrecognized step key."""
+        result = self.provider.is_step_completed(
+            db, loy_store.id, "loyalty.unknown_step"
+        )
+        assert result is False