feat: add docker_container node type with migrations and fixes

- Fix CONTAINER_MODE_TYPES to only include proxmox and docker_host (not vm/lxc)
- Add DB migration: existing proxmox nodes get container_mode=1 (they were always containers)
- Add DB migration: legacy 'docker' type renamed to 'docker_container'
- Update canvasStore tests: parent nodes need container_mode=true to nest children
- Fix updateNode test: pass absolute position so relative recalc yields expected coords
- Add backend tests for both migrations (test_docker_migration.py)

backend/tests/test_docker_migration.py

@@ -0,0 +1,96 @@
+"""
+Tests for docker type rename and proxmox container_mode migrations.
+"""
+import os
+
+os.environ.setdefault("SECRET_KEY", "test-only-secret-key-not-for-production")
+
+import pytest
+from sqlalchemy.ext.asyncio import create_async_engine
+
+TEST_DB_URL = "sqlite+aiosqlite:///:memory:"
+
+
+async def _setup_table(conn):
+    await conn.exec_driver_sql("""
+        CREATE TABLE IF NOT EXISTS nodes (
+            id TEXT PRIMARY KEY,
+            type TEXT NOT NULL DEFAULT 'generic',
+            label TEXT NOT NULL DEFAULT '',
+            container_mode BOOLEAN NOT NULL DEFAULT 0
+        )
+    """)
+
+
+async def _run_migrations(conn):
+    await conn.exec_driver_sql(
+        "UPDATE nodes SET container_mode = 1 WHERE type = 'proxmox' AND container_mode = 0"
+    )
+    await conn.exec_driver_sql(
+        "UPDATE nodes SET type = 'docker_container' WHERE type = 'docker'"
+    )
+
+
+@pytest.mark.asyncio
+async def test_proxmox_container_mode_set_to_true():
+    engine = create_async_engine(TEST_DB_URL)
+    async with engine.begin() as conn:
+        await _setup_table(conn)
+        await conn.exec_driver_sql(
+            "INSERT INTO nodes (id, type, label, container_mode) VALUES ('p1', 'proxmox', 'PVE', 0)"
+        )
+        await _run_migrations(conn)
+        row = (await conn.exec_driver_sql("SELECT container_mode FROM nodes WHERE id = 'p1'")).fetchone()
+        assert row[0] == 1
+
+
+@pytest.mark.asyncio
+async def test_proxmox_already_true_unchanged():
+    engine = create_async_engine(TEST_DB_URL)
+    async with engine.begin() as conn:
+        await _setup_table(conn)
+        await conn.exec_driver_sql(
+            "INSERT INTO nodes (id, type, label, container_mode) VALUES ('p2', 'proxmox', 'PVE', 1)"
+        )
+        await _run_migrations(conn)
+        row = (await conn.exec_driver_sql("SELECT container_mode FROM nodes WHERE id = 'p2'")).fetchone()
+        assert row[0] == 1
+
+
+@pytest.mark.asyncio
+async def test_non_proxmox_container_mode_untouched():
+    engine = create_async_engine(TEST_DB_URL)
+    async with engine.begin() as conn:
+        await _setup_table(conn)
+        await conn.exec_driver_sql(
+            "INSERT INTO nodes (id, type, label, container_mode) VALUES ('s1', 'server', 'Srv', 0)"
+        )
+        await _run_migrations(conn)
+        row = (await conn.exec_driver_sql("SELECT container_mode FROM nodes WHERE id = 's1'")).fetchone()
+        assert row[0] == 0
+
+
+@pytest.mark.asyncio
+async def test_docker_type_renamed_to_docker_container():
+    engine = create_async_engine(TEST_DB_URL)
+    async with engine.begin() as conn:
+        await _setup_table(conn)
+        await conn.exec_driver_sql(
+            "INSERT INTO nodes (id, type, label) VALUES ('d1', 'docker', 'My Docker')"
+        )
+        await _run_migrations(conn)
+        row = (await conn.exec_driver_sql("SELECT type FROM nodes WHERE id = 'd1'")).fetchone()
+        assert row[0] == 'docker_container'
+
+
+@pytest.mark.asyncio
+async def test_docker_host_type_untouched():
+    engine = create_async_engine(TEST_DB_URL)
+    async with engine.begin() as conn:
+        await _setup_table(conn)
+        await conn.exec_driver_sql(
+            "INSERT INTO nodes (id, type, label) VALUES ('d2', 'docker_host', 'Docker Host')"
+        )
+        await _run_migrations(conn)
+        row = (await conn.exec_driver_sql("SELECT type FROM nodes WHERE id = 'd2'")).fetchone()
+        assert row[0] == 'docker_host'