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/api/v1/vendor/__init__.py

@@ -20,6 +20,7 @@ from . import (
     content_pages,
     customers,
     dashboard,
+    email_settings,
     email_templates,
     features,
     info,
@@ -61,6 +62,7 @@ router.include_router(dashboard.router, tags=["vendor-dashboard"])
 router.include_router(profile.router, tags=["vendor-profile"])
 router.include_router(settings.router, tags=["vendor-settings"])
 router.include_router(email_templates.router, tags=["vendor-email-templates"])
+router.include_router(email_settings.router, tags=["vendor-email-settings"])
 router.include_router(onboarding.router, tags=["vendor-onboarding"])
 
 # Business operations (with prefixes: /products/*, /orders/*, etc.)