feat: add mandatory vendor onboarding wizard

Implement 4-step onboarding flow for new vendors after signup:
- Step 1: Company profile setup
- Step 2: Letzshop API configuration with connection testing
- Step 3: Product & order import CSV URL configuration
- Step 4: Historical order sync with progress bar

Key features:
- Blocks dashboard access until completed
- Step indicators with visual progress
- Resume capability (progress persisted in DB)
- Admin skip capability for support cases

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

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

alembic/versions/m1b2c3d4e5f6_add_vendor_onboarding_table.py

@@ -0,0 +1,72 @@
+"""add vendor onboarding table
+
+Revision ID: m1b2c3d4e5f6
+Revises: d7a4a3f06394
+Create Date: 2025-12-27 22:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'm1b2c3d4e5f6'
+down_revision: Union[str, None] = 'd7a4a3f06394'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table('vendor_onboarding',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('vendor_id', sa.Integer(), nullable=False),
+        # Overall status
+        sa.Column('status', sa.String(length=20), nullable=False, server_default='not_started'),
+        sa.Column('current_step', sa.String(length=30), nullable=False, server_default='company_profile'),
+        # Step 1: Company Profile
+        sa.Column('step_company_profile_completed', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        sa.Column('step_company_profile_completed_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('step_company_profile_data', sa.JSON(), nullable=True),
+        # Step 2: Letzshop API Configuration
+        sa.Column('step_letzshop_api_completed', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        sa.Column('step_letzshop_api_completed_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('step_letzshop_api_connection_verified', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        # Step 3: Product Import
+        sa.Column('step_product_import_completed', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        sa.Column('step_product_import_completed_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('step_product_import_csv_url_set', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        # Step 4: Order Sync
+        sa.Column('step_order_sync_completed', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        sa.Column('step_order_sync_completed_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('step_order_sync_job_id', sa.Integer(), nullable=True),
+        # Completion tracking
+        sa.Column('started_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('completed_at', sa.DateTime(timezone=True), nullable=True),
+        # Admin override
+        sa.Column('skipped_by_admin', sa.Boolean(), nullable=False, server_default=sa.text('0')),
+        sa.Column('skipped_at', sa.DateTime(timezone=True), nullable=True),
+        sa.Column('skipped_reason', sa.Text(), nullable=True),
+        sa.Column('skipped_by_user_id', sa.Integer(), nullable=True),
+        # Timestamps
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        # Constraints
+        sa.ForeignKeyConstraint(['vendor_id'], ['vendors.id'], ondelete='CASCADE'),
+        sa.ForeignKeyConstraint(['skipped_by_user_id'], ['users.id']),
+        sa.PrimaryKeyConstraint('id'),
+        sqlite_autoincrement=True
+    )
+    op.create_index(op.f('ix_vendor_onboarding_id'), 'vendor_onboarding', ['id'], unique=False)
+    op.create_index(op.f('ix_vendor_onboarding_vendor_id'), 'vendor_onboarding', ['vendor_id'], unique=True)
+    op.create_index(op.f('ix_vendor_onboarding_status'), 'vendor_onboarding', ['status'], unique=False)
+    op.create_index('idx_onboarding_vendor_status', 'vendor_onboarding', ['vendor_id', 'status'], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index('idx_onboarding_vendor_status', table_name='vendor_onboarding')
+    op.drop_index(op.f('ix_vendor_onboarding_status'), table_name='vendor_onboarding')
+    op.drop_index(op.f('ix_vendor_onboarding_vendor_id'), table_name='vendor_onboarding')
+    op.drop_index(op.f('ix_vendor_onboarding_id'), table_name='vendor_onboarding')
+    op.drop_table('vendor_onboarding')