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>

app/templates/vendor/onboarding.html

@@ -31,6 +31,7 @@
                 </button>
 
                 <!-- Language Selector -->
+                {# noqa: FE-006 - Custom language selector with flags, not suited for dropdown macro #}
                 <div class="relative" x-data="{ open: false }">
                     <button @click="open = !open"
                             class="flex items-center space-x-2 px-3 py-2 rounded-lg bg-white dark:bg-gray-700 border border-gray-200 dark:border-gray-600 hover:bg-gray-50 dark:hover:bg-gray-600 transition-colors">
@@ -280,6 +281,7 @@
                                 </div>
                                 <div>
                                     <label class="block text-sm text-gray-600 dark:text-gray-400" x-text="t('step3.preorder_days')"></label>
+                                    {# noqa: FE-008 - Simple number input, not a quantity stepper pattern #}
                                     <input type="number" x-model="formData.preorder_days" min="0" max="30"
                                            class="mt-1 block w-full rounded-md border-gray-300 dark:border-gray-600 dark:bg-gray-700 dark:text-white shadow-sm focus:border-purple-500 focus:ring-purple-500" />
                                     <p class="mt-1 text-xs text-gray-500 dark:text-gray-400" x-text="t('step3.preorder_days_help')"></p>