feat(ssh): add multi-organization support for certificate signing

Add support for users who belong to multiple organizations to select
which organization's CA should sign their SSH certificates.

Changes:
- CLI: Add --org-id and --list-orgs options for organization selection
- API: Return MULTIPLE_ORGS_AMBIGUOUS error when org selection needed
- API: Add /users/me/organizations/simple endpoint for CLI org listing
- DB: Add organization_id to certificate_audit_logs for better tracking
- Include organization_name in certificate response for clarity

migrations/versions/8f2d9e4a7c1b_add_org_id_to_cert_audit_logs.py

@@ -0,0 +1,50 @@
+"""Add organization_id to certificate_audit_logs.
+
+Revision ID: 8f2d9e4a7c1b
+Revises: b4cd6c6b3b1c
+Create Date: 2026-04-23 07:30:00.000000
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '8f2d9e4a7c1b'
+down_revision = 'b4cd6c6b3b1c'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # Add organization_id column to certificate_audit_logs
+    op.add_column(
+        'certificate_audit_logs',
+        sa.Column('organization_id', sa.String(length=36), nullable=True)
+    )
+    
+    # Create index on organization_id
+    op.create_index(
+        'idx_cert_audit_org',
+        'certificate_audit_logs',
+        ['organization_id']
+    )
+    
+    # Create foreign key constraint
+    op.create_foreign_key(
+        'fk_cert_audit_log_organization',
+        'certificate_audit_logs',
+        'organizations',
+        ['organization_id'],
+        ['id']
+    )
+
+
+def downgrade():
+    # Drop foreign key constraint
+    op.drop_constraint('fk_cert_audit_log_organization', 'certificate_audit_logs', type_='foreignkey')
+    
+    # Drop index
+    op.drop_index('idx_cert_audit_org', 'certificate_audit_logs')
+    
+    # Drop organization_id column
+    op.drop_column('certificate_audit_logs', 'organization_id')