feat: add email settings with database overrides for admin and vendor

Platform Email Settings (Admin):
- Add GET/PUT/DELETE /admin/settings/email/* endpoints
- Settings stored in admin_settings table override .env values
- Support all providers: SMTP, SendGrid, Mailgun, Amazon SES
- Edit mode UI with provider-specific configuration forms
- Reset to .env defaults functionality
- Test email to verify configuration

Vendor Email Settings:
- Add VendorEmailSettings model with one-to-one vendor relationship
- Migration: v0a1b2c3d4e5_add_vendor_email_settings.py
- Service: vendor_email_settings_service.py with tier validation
- API endpoints: /vendor/email-settings/* (CRUD, status, verify)
- Email tab in vendor settings page with full configuration
- Warning banner until email is configured (like billing warnings)
- Premium providers (SendGrid, Mailgun, SES) tier-gated to Business+

Email Service Updates:
- get_platform_email_config(db) checks DB first, then .env
- Configurable provider classes accept config dict
- EmailService uses database-aware providers
- Vendor emails use vendor's own SMTP (Wizamart doesn't pay)
- "Powered by Wizamart" footer for Essential/Professional tiers
- White-label (no footer) for Business/Enterprise tiers

Other:
- Add scripts/install.py for first-time platform setup
- Add make install target
- Update init-prod to include email template seeding

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

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

static/vendor/js/orders.js

@@ -312,9 +312,11 @@ function vendorOrders() {
          */
         formatPrice(cents) {
             if (!cents && cents !== 0) return '-';
-            return new Intl.NumberFormat('de-DE', {
+            const locale = window.VENDOR_CONFIG?.locale || 'en-GB';
+            const currency = window.VENDOR_CONFIG?.currency || 'EUR';
+            return new Intl.NumberFormat(locale, {
                 style: 'currency',
-                currency: 'EUR'
+                currency: currency
             }).format(cents / 100);
         },
 
@@ -323,7 +325,8 @@ function vendorOrders() {
          */
         formatDate(dateStr) {
             if (!dateStr) return '-';
-            return new Date(dateStr).toLocaleDateString('de-DE', {
+            const locale = window.VENDOR_CONFIG?.locale || 'en-GB';
+            return new Date(dateStr).toLocaleDateString(locale, {
                 year: 'numeric',
                 month: 'short',
                 day: 'numeric',