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>

alembic/versions/v0a1b2c3d4e5_add_vendor_email_settings.py

@@ -0,0 +1,102 @@
+# alembic/versions/v0a1b2c3d4e5_add_vendor_email_settings.py
+"""Add vendor email settings table.
+
+Revision ID: v0a1b2c3d4e5
+Revises: u9c0d1e2f3g4
+Create Date: 2026-01-05
+
+Changes:
+- Create vendor_email_settings table for vendor SMTP/email provider configuration
+- Vendors must configure this to send transactional emails
+- Premium providers (SendGrid, Mailgun, SES) are tier-gated (Business+)
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "v0a1b2c3d4e5"
+down_revision = "u9c0d1e2f3g4"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Create vendor_email_settings table
+    op.create_table(
+        "vendor_email_settings",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("vendor_id", sa.Integer(), nullable=False),
+        # Sender Identity
+        sa.Column("from_email", sa.String(255), nullable=False),
+        sa.Column("from_name", sa.String(100), nullable=False),
+        sa.Column("reply_to_email", sa.String(255), nullable=True),
+        # Signature/Footer
+        sa.Column("signature_text", sa.Text(), nullable=True),
+        sa.Column("signature_html", sa.Text(), nullable=True),
+        # Provider Configuration
+        sa.Column("provider", sa.String(20), nullable=False, default="smtp"),
+        # SMTP Settings
+        sa.Column("smtp_host", sa.String(255), nullable=True),
+        sa.Column("smtp_port", sa.Integer(), nullable=True, default=587),
+        sa.Column("smtp_username", sa.String(255), nullable=True),
+        sa.Column("smtp_password", sa.String(500), nullable=True),
+        sa.Column("smtp_use_tls", sa.Boolean(), nullable=False, default=True),
+        sa.Column("smtp_use_ssl", sa.Boolean(), nullable=False, default=False),
+        # SendGrid Settings
+        sa.Column("sendgrid_api_key", sa.String(500), nullable=True),
+        # Mailgun Settings
+        sa.Column("mailgun_api_key", sa.String(500), nullable=True),
+        sa.Column("mailgun_domain", sa.String(255), nullable=True),
+        # Amazon SES Settings
+        sa.Column("ses_access_key_id", sa.String(100), nullable=True),
+        sa.Column("ses_secret_access_key", sa.String(500), nullable=True),
+        sa.Column("ses_region", sa.String(50), nullable=True, default="eu-west-1"),
+        # Status & Verification
+        sa.Column("is_configured", sa.Boolean(), nullable=False, default=False),
+        sa.Column("is_verified", sa.Boolean(), nullable=False, default=False),
+        sa.Column("last_verified_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("verification_error", sa.Text(), nullable=True),
+        # Timestamps
+        sa.Column("created_at", sa.DateTime(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(), nullable=False),
+        # Constraints
+        sa.PrimaryKeyConstraint("id"),
+        sa.ForeignKeyConstraint(
+            ["vendor_id"],
+            ["vendors.id"],
+            name="fk_vendor_email_settings_vendor_id",
+            ondelete="CASCADE",
+        ),
+        sa.UniqueConstraint("vendor_id", name="uq_vendor_email_settings_vendor_id"),
+    )
+
+    # Create indexes
+    op.create_index(
+        "ix_vendor_email_settings_id",
+        "vendor_email_settings",
+        ["id"],
+        unique=False,
+    )
+    op.create_index(
+        "ix_vendor_email_settings_vendor_id",
+        "vendor_email_settings",
+        ["vendor_id"],
+        unique=True,
+    )
+    op.create_index(
+        "idx_vendor_email_settings_configured",
+        "vendor_email_settings",
+        ["vendor_id", "is_configured"],
+    )
+
+
+def downgrade() -> None:
+    # Drop indexes
+    op.drop_index("idx_vendor_email_settings_configured", table_name="vendor_email_settings")
+    op.drop_index("ix_vendor_email_settings_vendor_id", table_name="vendor_email_settings")
+    op.drop_index("ix_vendor_email_settings_id", table_name="vendor_email_settings")
+
+    # Drop table
+    op.drop_table("vendor_email_settings")