feat(boards): Store gateway config per board

Move gateway configuration into board settings and wire agent\nprovisioning, heartbeat templates, and gateway status lookups\nto use board-specific gateway settings. Adds board_id on agents\nand UI updates for board-scoped selection.\n\nCo-Authored-By: Claude <noreply@anthropic.com>

backend/alembic/versions/f1a2b3c4d5e6_add_board_gateway_config.py

@@ -0,0 +1,47 @@
+"""add board gateway config
+
+Revision ID: f1a2b3c4d5e6
+Revises: e4f5a6b7c8d9
+Create Date: 2026-02-04 00:00:00.000000
+
+"""
+
+from __future__ import annotations
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "f1a2b3c4d5e6"
+down_revision = "e4f5a6b7c8d9"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("boards", sa.Column("gateway_url", sa.String(), nullable=True))
+    op.add_column("boards", sa.Column("gateway_token", sa.String(), nullable=True))
+    op.add_column(
+        "boards", sa.Column("gateway_main_session_key", sa.String(), nullable=True)
+    )
+    op.add_column(
+        "boards", sa.Column("gateway_workspace_root", sa.String(), nullable=True)
+    )
+
+    op.add_column("agents", sa.Column("board_id", sa.Uuid(), nullable=True))
+    op.create_foreign_key(
+        "agents_board_id_fkey", "agents", "boards", ["board_id"], ["id"]
+    )
+    op.create_index(op.f("ix_agents_board_id"), "agents", ["board_id"], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index(op.f("ix_agents_board_id"), table_name="agents")
+    op.drop_constraint("agents_board_id_fkey", "agents", type_="foreignkey")
+    op.drop_column("agents", "board_id")
+
+    op.drop_column("boards", "gateway_workspace_root")
+    op.drop_column("boards", "gateway_main_session_key")
+    op.drop_column("boards", "gateway_token")
+    op.drop_column("boards", "gateway_url")