feat: form-input library with schema parsing and endpoint

backend/migrations/versions/b7e2d4a1c9f3_cache_form_schema.py

@@ -0,0 +1,32 @@
+"""cache form schema per flow version
+
+Revision ID: b7e2d4a1c9f3
+Revises: a3f1c9e2b4d7
+Create Date: 2026-09-11 20:30:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+import sqlmodel  # noqa: F401 - autogenerate renders sqlmodel.* column types
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'b7e2d4a1c9f3'
+down_revision: Union[str, Sequence[str], None] = 'a3f1c9e2b4d7'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    op.add_column(
+        "flow_versions",
+        sa.Column("input_schema", sa.JSON(), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    op.drop_column("flow_versions", "input_schema")