feat: complete billing module self-containment

Migrate billing module routes to self-contained structure:

- routes/api/admin.py - Admin API endpoints
- routes/api/vendor.py - Vendor API endpoints
- routes/pages/ - Page routes (placeholder)
- models/subscription.py - Subscription model (moved)
- schemas/subscription.py - Pydantic schemas (moved)
- locales/ - Translations (en, de, fr, lu)

Removed legacy route files:
- app/modules/billing/routes/admin.py
- app/modules/billing/routes/vendor.py

Updated __init__.py files to use new structure.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/billing/routes/api/vendor.py

@@ -0,0 +1,216 @@
+# app/modules/billing/routes/vendor.py
+"""
+Billing module vendor routes.
+
+This module wraps the existing vendor billing routes and adds
+module-based access control. The actual route implementations remain
+in app/api/v1/vendor/billing.py for now, but are accessed through
+this module-aware router.
+
+Future: Move all route implementations here for full module isolation.
+"""
+
+import logging
+
+from fastapi import APIRouter, Depends, Query
+from pydantic import BaseModel
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_current_vendor_api, require_module_access
+from app.core.config import settings
+from app.core.database import get_db
+from app.services.billing_service import billing_service
+from app.services.subscription_service import subscription_service
+from models.database.user import User
+
+logger = logging.getLogger(__name__)
+
+# Vendor router with module access control
+vendor_router = APIRouter(
+    prefix="/billing",
+    dependencies=[Depends(require_module_access("billing"))],
+)
+
+
+# ============================================================================
+# Schemas (re-exported from original module)
+# ============================================================================
+
+
+class SubscriptionStatusResponse(BaseModel):
+    """Current subscription status and usage."""
+
+    tier_code: str
+    tier_name: str
+    status: str
+    is_trial: bool
+    trial_ends_at: str | None = None
+    period_start: str | None = None
+    period_end: str | None = None
+    cancelled_at: str | None = None
+    cancellation_reason: str | None = None
+
+    # Usage
+    orders_this_period: int
+    orders_limit: int | None
+    orders_remaining: int | None
+    products_count: int
+    products_limit: int | None
+    products_remaining: int | None
+    team_count: int
+    team_limit: int | None
+    team_remaining: int | None
+
+    # Payment
+    has_payment_method: bool
+    last_payment_error: str | None = None
+
+    class Config:
+        from_attributes = True
+
+
+class TierResponse(BaseModel):
+    """Subscription tier information."""
+
+    code: str
+    name: str
+    description: str | None = None
+    price_monthly_cents: int
+    price_annual_cents: int | None = None
+    orders_per_month: int | None = None
+    products_limit: int | None = None
+    team_members: int | None = None
+    features: list[str] = []
+    is_current: bool = False
+    can_upgrade: bool = False
+    can_downgrade: bool = False
+
+
+class TierListResponse(BaseModel):
+    """List of available tiers."""
+
+    tiers: list[TierResponse]
+    current_tier: str
+
+
+class InvoiceResponse(BaseModel):
+    """Invoice information."""
+
+    id: int
+    invoice_number: str | None = None
+    invoice_date: str
+    due_date: str | None = None
+    total_cents: int
+    amount_paid_cents: int
+    currency: str
+    status: str
+    pdf_url: str | None = None
+    hosted_url: str | None = None
+
+
+class InvoiceListResponse(BaseModel):
+    """List of invoices."""
+
+    invoices: list[InvoiceResponse]
+    total: int
+
+
+# ============================================================================
+# Core Billing Endpoints
+# ============================================================================
+
+
+@vendor_router.get("/subscription", response_model=SubscriptionStatusResponse)
+def get_subscription_status(
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Get current subscription status and usage metrics."""
+    vendor_id = current_user.token_vendor_id
+
+    usage = subscription_service.get_usage_summary(db, vendor_id)
+    subscription, tier = billing_service.get_subscription_with_tier(db, vendor_id)
+
+    return SubscriptionStatusResponse(
+        tier_code=subscription.tier,
+        tier_name=tier.name if tier else subscription.tier.title(),
+        status=subscription.status.value,
+        is_trial=subscription.is_in_trial(),
+        trial_ends_at=subscription.trial_ends_at.isoformat()
+        if subscription.trial_ends_at
+        else None,
+        period_start=subscription.period_start.isoformat()
+        if subscription.period_start
+        else None,
+        period_end=subscription.period_end.isoformat()
+        if subscription.period_end
+        else None,
+        cancelled_at=subscription.cancelled_at.isoformat()
+        if subscription.cancelled_at
+        else None,
+        cancellation_reason=subscription.cancellation_reason,
+        orders_this_period=usage.orders_this_period,
+        orders_limit=usage.orders_limit,
+        orders_remaining=usage.orders_remaining,
+        products_count=usage.products_count,
+        products_limit=usage.products_limit,
+        products_remaining=usage.products_remaining,
+        team_count=usage.team_count,
+        team_limit=usage.team_limit,
+        team_remaining=usage.team_remaining,
+        has_payment_method=bool(subscription.stripe_payment_method_id),
+        last_payment_error=subscription.last_payment_error,
+    )
+
+
+@vendor_router.get("/tiers", response_model=TierListResponse)
+def get_available_tiers(
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Get available subscription tiers for upgrade/downgrade."""
+    vendor_id = current_user.token_vendor_id
+    subscription = subscription_service.get_or_create_subscription(db, vendor_id)
+    current_tier = subscription.tier
+
+    tier_list, _ = billing_service.get_available_tiers(db, current_tier)
+
+    tier_responses = [TierResponse(**tier_data) for tier_data in tier_list]
+
+    return TierListResponse(tiers=tier_responses, current_tier=current_tier)
+
+
+@vendor_router.get("/invoices", response_model=InvoiceListResponse)
+def get_invoices(
+    skip: int = Query(0, ge=0),
+    limit: int = Query(20, ge=1, le=100),
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Get invoice history."""
+    vendor_id = current_user.token_vendor_id
+
+    invoices, total = billing_service.get_invoices(db, vendor_id, skip=skip, limit=limit)
+
+    invoice_responses = [
+        InvoiceResponse(
+            id=inv.id,
+            invoice_number=inv.invoice_number,
+            invoice_date=inv.invoice_date.isoformat(),
+            due_date=inv.due_date.isoformat() if inv.due_date else None,
+            total_cents=inv.total_cents,
+            amount_paid_cents=inv.amount_paid_cents,
+            currency=inv.currency,
+            status=inv.status,
+            pdf_url=inv.invoice_pdf_url,
+            hosted_url=inv.hosted_invoice_url,
+        )
+        for inv in invoices
+    ]
+
+    return InvoiceListResponse(invoices=invoice_responses, total=total)
+
+
+# NOTE: Additional endpoints (checkout, portal, cancel, addons, etc.)
+# are still handled by app/api/v1/vendor/billing.py for now.
+# They can be migrated here as part of a larger refactoring effort.