fix: add missing schema columns and Alembic model imports

- Added 4 missing columns to _ensure_translation_jobs_columns() inline
  migration: target_language_column, target_source_column,
  target_source_language_column, disable_reasoning — these were in the
  SQLAlchemy model but had no Alembic migration or _ensure_*() coverage
- Added missing api_key, assistant, clean_release model imports to
  alembic/env.py so autogenerate can see all tables

backend/alembic/env.py

@@ -30,7 +30,10 @@ from src.models.mapping import Base
 
 # Import ALL model modules so their tables are registered in Base.metadata
 from src.models import (  # noqa: F401
+    api_key,
+    assistant,
     auth,
+    clean_release,
     dashboard,
     dataset_review_pkg,
     filter_state,

backend/src/core/database.py

@@ -527,6 +527,71 @@ def _ensure_translation_jobs_columns(bind_engine):
                     extra={"error": str(migration_error)},
                 )
 
+        # Columns added to model AFTER initial Alembic migration — no Alembic migration exists
+        if "target_language_column" not in existing_columns:
+            try:
+                with bind_engine.begin() as connection:
+                    connection.execute(
+                        text(
+                            "ALTER TABLE translation_jobs "
+                            "ADD COLUMN target_language_column VARCHAR"
+                        )
+                    )
+                logger.reflect("Added target_language_column to translation_jobs")
+            except Exception as migration_error:
+                logger.explore(
+                    "Failed to add target_language_column to translation_jobs",
+                    extra={"error": str(migration_error)},
+                )
+
+        if "target_source_column" not in existing_columns:
+            try:
+                with bind_engine.begin() as connection:
+                    connection.execute(
+                        text(
+                            "ALTER TABLE translation_jobs "
+                            "ADD COLUMN target_source_column VARCHAR"
+                        )
+                    )
+                logger.reflect("Added target_source_column to translation_jobs")
+            except Exception as migration_error:
+                logger.explore(
+                    "Failed to add target_source_column to translation_jobs",
+                    extra={"error": str(migration_error)},
+                )
+
+        if "target_source_language_column" not in existing_columns:
+            try:
+                with bind_engine.begin() as connection:
+                    connection.execute(
+                        text(
+                            "ALTER TABLE translation_jobs "
+                            "ADD COLUMN target_source_language_column VARCHAR"
+                        )
+                    )
+                logger.reflect("Added target_source_language_column to translation_jobs")
+            except Exception as migration_error:
+                logger.explore(
+                    "Failed to add target_source_language_column to translation_jobs",
+                    extra={"error": str(migration_error)},
+                )
+
+        if "disable_reasoning" not in existing_columns:
+            try:
+                with bind_engine.begin() as connection:
+                    connection.execute(
+                        text(
+                            "ALTER TABLE translation_jobs "
+                            "ADD COLUMN disable_reasoning BOOLEAN NOT NULL DEFAULT FALSE"
+                        )
+                    )
+                logger.reflect("Added disable_reasoning column to translation_jobs")
+            except Exception as migration_error:
+                logger.explore(
+                    "Failed to add disable_reasoning to translation_jobs",
+                    extra={"error": str(migration_error)},
+                )
+
 
 def _ensure_dataset_review_session_columns(bind_engine):
     with belief_scope("_ensure_dataset_review_session_columns"):