feat: wire Google Wallet into loyalty enrollment, stamps, and points flows

Connect the fully-implemented Google Wallet service to the loyalty module:
- Create wallet class/object on customer enrollment
- Sync wallet passes on stamp and points operations
- Expose wallet URLs in storefront API responses
- Add conditional "Add to Google Wallet" buttons on dashboard and enroll-success pages
- Use platform-wide env var config (not per-merchant DB column)
- Add Google service account patterns to .gitignore
- Add LOYALTY_GOOGLE_* fields to app Settings
- Update deployment docs and add local testing guide

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

app/modules/loyalty/static/storefront/js/loyalty-dashboard.js

@@ -12,6 +12,9 @@ function customerLoyaltyDashboard() {
         transactions: [],
         locations: [],
 
+        // Wallet
+        walletUrls: { google_wallet_url: null, apple_wallet_url: null },
+
         // UI state
         loading: false,
         showBarcode: false,
@@ -43,6 +46,7 @@ function customerLoyaltyDashboard() {
                     this.program = response.program;
                     this.rewards = response.program?.points_rewards || [];
                     this.locations = response.locations || [];
+                    this.walletUrls = response.wallet_urls || { google_wallet_url: null, apple_wallet_url: null };
                     console.log('Loyalty card loaded:', this.card?.card_number);
                 }
             } catch (error) {