fix: handle Alembic offline mode in migration _column_exists() helper

The _column_exists() helper in migrations 026-029 calls conn.execute()
which returns None in Alembic's offline/SQL mode (--sql flag), causing
AttributeError on result.scalar(). Add context.is_offline_mode() guard
to skip the idempotency check in offline mode and unconditionally emit
the DDL statements.

Fixes: Validate CI step 'alembic upgrade head --sql' failure.

alembic/versions/026_add_user_profile_fields.py

@@ -10,7 +10,7 @@ Create Date: 2026-07-05
 
 import sqlalchemy as sa
 
-from alembic import op
+from alembic import context, op
 
 revision = "026"
 down_revision = "025"
@@ -19,6 +19,8 @@ depends_on = None
 
 
 def _column_exists(table: str, column: str) -> bool:
+    if context.is_offline_mode():
+        return False
     conn = op.get_bind()
     result = conn.execute(
         sa.text(

alembic/versions/027_add_user_ban_fields.py

@@ -10,7 +10,7 @@ Create Date: 2026-07-05
 
 import sqlalchemy as sa
 
-from alembic import op
+from alembic import context, op
 
 revision = "027"
 down_revision = "026"
@@ -19,6 +19,8 @@ depends_on = None
 
 
 def _column_exists(table: str, column: str) -> bool:
+    if context.is_offline_mode():
+        return False
     conn = op.get_bind()
     result = conn.execute(
         sa.text(

alembic/versions/028_add_user_admin_fields.py

@@ -10,7 +10,7 @@ Create Date: 2026-07-05
 
 import sqlalchemy as sa
 
-from alembic import op
+from alembic import context, op
 
 revision = "028"
 down_revision = "027"
@@ -19,6 +19,8 @@ depends_on = None
 
 
 def _column_exists(table: str, column: str) -> bool:
+    if context.is_offline_mode():
+        return False
     conn = op.get_bind()
     result = conn.execute(
         sa.text(

alembic/versions/029_add_user_phone.py

@@ -10,7 +10,7 @@ Create Date: 2026-07-05
 
 import sqlalchemy as sa
 
-from alembic import op
+from alembic import context, op
 
 revision = "029"
 down_revision = "028"
@@ -19,6 +19,8 @@ depends_on = None
 
 
 def _column_exists(table: str, column: str) -> bool:
+    if context.is_offline_mode():
+        return False
     conn = op.get_bind()
     result = conn.execute(
         sa.text(