feat: add database migration for platform field

Generate Alembic migration to add platform column to rooms and meetings
tables enabling multi-platform video conferencing support.

- Add platform column to meeting table with whereby default
- Add platform column to room table with whereby default
- Migration tested successfully with alembic upgrade head

🤖 Generated with [Claude Code](https://claude.ai/code)

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

server/migrations/versions/35e035defa85_add_platform_field_to_rooms_and_meetings.py

@@ -0,0 +1,44 @@
+"""Add platform field to rooms and meetings
+
+Revision ID: 35e035defa85
+Revises: 61882a919591
+Create Date: 2025-09-02 16:08:55.205173
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "35e035defa85"
+down_revision: Union[str, None] = "61882a919591"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table("meeting", schema=None) as batch_op:
+        batch_op.add_column(
+            sa.Column("platform", sa.String(), server_default="whereby", nullable=False)
+        )
+
+    with op.batch_alter_table("room", schema=None) as batch_op:
+        batch_op.add_column(
+            sa.Column("platform", sa.String(), server_default="whereby", nullable=False)
+        )
+
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table("room", schema=None) as batch_op:
+        batch_op.drop_column("platform")
+
+    with op.batch_alter_table("meeting", schema=None) as batch_op:
+        batch_op.drop_column("platform")
+
+    # ### end Alembic commands ###