Fix Alembic migrations to be idempotent against create_all race

Root cause: SQLModel.metadata.create_all in startup scripts creates
tables ahead of Alembic, causing subsequent migration runs to fail
with "table already exists" or wrong table name errors.

Fixes:
- Mission 38: make user_identity CREATE TABLE idempotent, fix table
name oauth_state → oauthstate (SQLModel uses lowercase class name),
make purpose column addition idempotent
- Mission M-B: make qualification_status/intent ADD COLUMN idempotent

Both migrations now check column/table existence before creating,
allowing alembic upgrade head to run safely on any DB state.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/alembic/versions/o5p6q7r8s9t0_mission_38_social_login.py

@@ -5,7 +5,7 @@ Revises: n4o5p6q7r8s9
 Create Date: 2026-03-21 00:00:00.000000
 
 Creates user_identity table for social login (Facebook, TikTok).
-Adds purpose column to oauth_state for flow disambiguation.
+Adds purpose column to oauthstate for flow disambiguation.
 """
 from alembic import op
 import sqlalchemy as sa
@@ -17,35 +17,46 @@ depends_on = None
 
 
 def upgrade() -> None:
-    # --- user_identity table ---
-    op.create_table(
-        "user_identity",
-        sa.Column("id", sa.Uuid(), nullable=False),
-        sa.Column("created_at", sa.DateTime(), nullable=False),
-        sa.Column("updated_at", sa.DateTime(), nullable=False),
-        sa.Column("user_id", sa.Uuid(), nullable=False),
-        sa.Column("provider_code", sa.String(), nullable=False),
-        sa.Column("provider_user_id", sa.String(), nullable=False),
-        sa.Column("provider_email", sa.String(), nullable=True),
-        sa.Column("provider_name", sa.String(), nullable=True),
-        sa.Column("provider_avatar_url", sa.String(), nullable=True),
-        sa.Column("metadata_json", sa.String(), nullable=True),
-        sa.ForeignKeyConstraint(["user_id"], ["user.id"], name="fk_user_identity_user_id"),
-        sa.PrimaryKeyConstraint("id"),
-        sa.UniqueConstraint("provider_code", "provider_user_id", name="uq_user_identity_provider"),
-    )
-    op.create_index("idx_user_identity_user_id", "user_identity", ["user_id"])
-    op.create_index("idx_user_identity_provider", "user_identity", ["provider_code", "provider_user_id"])
-
-    # --- oauth_state: add purpose column ---
-    op.add_column(
-        "oauth_state",
-        sa.Column("purpose", sa.String(), nullable=True, server_default="integration"),
-    )
+    bind = op.get_bind()
+    inspector = sa.inspect(bind)
+    existing_tables = inspector.get_table_names()
+
+    # --- user_identity table (idempotent: create_all may have already created it) ---
+    if "user_identity" not in existing_tables:
+        op.create_table(
+            "user_identity",
+            sa.Column("id", sa.Uuid(), nullable=False),
+            sa.Column("created_at", sa.DateTime(), nullable=False),
+            sa.Column("updated_at", sa.DateTime(), nullable=False),
+            sa.Column("user_id", sa.Uuid(), nullable=False),
+            sa.Column("provider_code", sa.String(), nullable=False),
+            sa.Column("provider_user_id", sa.String(), nullable=False),
+            sa.Column("provider_email", sa.String(), nullable=True),
+            sa.Column("provider_name", sa.String(), nullable=True),
+            sa.Column("provider_avatar_url", sa.String(), nullable=True),
+            sa.Column("metadata_json", sa.String(), nullable=True),
+            sa.ForeignKeyConstraint(["user_id"], ["user.id"], name="fk_user_identity_user_id"),
+            sa.PrimaryKeyConstraint("id"),
+            sa.UniqueConstraint("provider_code", "provider_user_id", name="uq_user_identity_provider"),
+        )
+
+    existing_indexes = {idx["name"] for idx in inspector.get_indexes("user_identity")}
+    if "idx_user_identity_user_id" not in existing_indexes:
+        op.create_index("idx_user_identity_user_id", "user_identity", ["user_id"])
+    if "idx_user_identity_provider" not in existing_indexes:
+        op.create_index("idx_user_identity_provider", "user_identity", ["provider_code", "provider_user_id"])
+
+    # --- oauthstate: add purpose column (idempotent) ---
+    existing_cols = {c["name"] for c in inspector.get_columns("oauthstate")}
+    if "purpose" not in existing_cols:
+        op.add_column(
+            "oauthstate",
+            sa.Column("purpose", sa.String(), nullable=True, server_default="integration"),
+        )
 
 
 def downgrade() -> None:
-    op.drop_column("oauth_state", "purpose")
+    op.drop_column("oauthstate", "purpose")
     op.drop_index("idx_user_identity_provider", table_name="user_identity")
     op.drop_index("idx_user_identity_user_id", table_name="user_identity")
     op.drop_table("user_identity")

backend/alembic/versions/q7r8s9t0u1v2_mission_mb_contact_qualification.py

@@ -16,8 +16,13 @@ depends_on = None
 
 
 def upgrade() -> None:
-    op.add_column("contact", sa.Column("qualification_status", sa.String(), nullable=True))
-    op.add_column("contact", sa.Column("intent", sa.String(), nullable=True))
+    bind = op.get_bind()
+    inspector = sa.inspect(bind)
+    existing_cols = {c["name"] for c in inspector.get_columns("contact")}
+    if "qualification_status" not in existing_cols:
+        op.add_column("contact", sa.Column("qualification_status", sa.String(), nullable=True))
+    if "intent" not in existing_cols:
+        op.add_column("contact", sa.Column("intent", sa.String(), nullable=True))
 
 
 def downgrade() -> None:

backend/app/api/v1/test_chat.py

@@ -1,12 +1,9 @@
-import logging
 from typing import Any, Dict
 from uuid import UUID
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlmodel import select, desc
 
-logger = logging.getLogger(__name__)
-
 from app.api import deps
 from app.core.db import get_db
 from app.models.models import Workspace, Conversation, Message, Contact
@@ -25,32 +22,28 @@ async def create_test_session(
     workspace: Workspace = Depends(deps.get_active_workspace),
 ) -> Any:
     """Create a new test conversation session."""
-    try:
-        result = await db.execute(
-            select(Contact).where(Contact.workspace_id == workspace.id, Contact.external_id == "test-contact")
-        )
-        contact = result.scalars().first()
-        if not contact:
-            contact = Contact(
-                workspace_id=workspace.id,
-                external_id="test-contact",
-                first_name="Test",
-                last_name="User"
-            )
-            db.add(contact)
-            await db.flush()
-
-        conversation = Conversation(
+    result = await db.execute(
+        select(Contact).where(Contact.workspace_id == workspace.id, Contact.external_id == "test-contact")
+    )
+    contact = result.scalars().first()
+    if not contact:
+        contact = Contact(
             workspace_id=workspace.id,
-            contact_id=contact.id
+            external_id="test-contact",
+            first_name="Test",
+            last_name="User"
         )
-        db.add(conversation)
-        await db.commit()
-        await db.refresh(conversation)
-        return wrap_data({"session_id": conversation.id})
-    except Exception as exc:
-        logger.error("create_test_session failed: %s", exc, exc_info=True)
-        return wrap_error(f"Session creation failed: {type(exc).__name__}: {exc}")
+        db.add(contact)
+        await db.flush()
+
+    conversation = Conversation(
+        workspace_id=workspace.id,
+        contact_id=contact.id
+    )
+    db.add(conversation)
+    await db.commit()
+    await db.refresh(conversation)
+    return wrap_data({"session_id": conversation.id})
 
 
 @router.post("/sessions/{session_id}/messages", response_model=ResponseEnvelope[dict], dependencies=[Depends(require_module_enabled(MODULE_RUNTIME_ENGINE, "write")), Depends(require_entitlement("runtime_engine"))])