feat: add customer profile, VAT alignment, and fix shop auth

Customer Profile:
- Add profile API (GET/PUT /api/v1/shop/profile)
- Add password change endpoint (PUT /api/v1/shop/profile/password)
- Implement full profile page with preferences and password sections
- Add CustomerPasswordChange schema

Shop Authentication Fixes:
- Add Authorization header to all shop account API calls
- Fix orders, order-detail, messages pages authentication
- Add proper redirect to login on 401 responses
- Fix toast message showing noqa comment in shop-layout.js

VAT Calculation:
- Add shared VAT utility (app/utils/vat.py)
- Add VAT fields to Order model (vat_regime, vat_rate, etc.)
- Align order VAT calculation with invoice settings
- Add migration for VAT fields on orders

Validation Framework:
- Fix base_validator.py with missing methods
- Add validate_file, output_results, get_exit_code methods
- Fix validate_all.py import issues

Documentation:
- Add launch-readiness.md tracking OMS status
- Update to 95% feature complete

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/services/invoice_service.py

@@ -477,6 +477,21 @@ class InvoiceService:
             .first()
         )
 
+    def get_invoice_by_order_id(
+        self, db: Session, vendor_id: int, order_id: int
+    ) -> Invoice | None:
+        """Get invoice by order ID."""
+        return (
+            db.query(Invoice)
+            .filter(
+                and_(
+                    Invoice.order_id == order_id,
+                    Invoice.vendor_id == vendor_id,
+                )
+            )
+            .first()
+        )
+
     def list_invoices(
         self,
         db: Session,