feat: git-based agent version reference and unified outdated badge (0.20.0)

SAC reads latest RDP/ssh-monitor versions from configured git repos for outdated detection, update targets, and settings test-git.

backend/alembic/versions/021_agent_git_release.py

@@ -0,0 +1,51 @@
+"""agent git release repos and version cache
+
+Revision ID: 021
+Revises: 020
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "021"
+down_revision: Union[str, None] = "020"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "ui_settings",
+        sa.Column("agent_rdp_git_repo_url", sa.String(length=512), nullable=True),
+    )
+    op.add_column(
+        "ui_settings",
+        sa.Column("agent_ssh_git_repo_url", sa.String(length=512), nullable=True),
+    )
+    op.add_column(
+        "ui_settings",
+        sa.Column("agent_git_branch", sa.String(length=64), nullable=False, server_default="main"),
+    )
+    op.add_column(
+        "ui_settings",
+        sa.Column("agent_git_rdp_version", sa.String(length=64), nullable=True),
+    )
+    op.add_column(
+        "ui_settings",
+        sa.Column("agent_git_ssh_version", sa.String(length=64), nullable=True),
+    )
+    op.add_column(
+        "ui_settings",
+        sa.Column("agent_git_fetched_at", sa.DateTime(timezone=True), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("ui_settings", "agent_git_fetched_at")
+    op.drop_column("ui_settings", "agent_git_ssh_version")
+    op.drop_column("ui_settings", "agent_git_rdp_version")
+    op.drop_column("ui_settings", "agent_git_branch")
+    op.drop_column("ui_settings", "agent_ssh_git_repo_url")
+    op.drop_column("ui_settings", "agent_rdp_git_repo_url")