fix(billing): address code review feedback

- Use DECIMAL instead of FLOAT for monetary columns in ALTER TABLE
- Simplify bind_param type string from concatenated to single literal
- Validate payment_status against ENUM values before CSS class injection
- Add provisioning failure logging when panel bootstrap fails
- Add comment explaining total_due/amount legacy fallback

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: iaretechnician <2749183+iaretechnician@users.noreply.github.com>

modules/billing/classes/BillingRepository.php

@@ -109,7 +109,7 @@ class BillingRepository
         if (!$stmt) return 0;
         $rawJson = is_array($data['raw_response']) ? json_encode($data['raw_response']) : (string)($data['raw_response'] ?? '');
         $stmt->bind_param(
-            'iiissdss' . 's',
+            'iiissdsss',
             $data['invoice_id'],
             $data['user_id'],
             $data['home_id'],