fix(reinstall): use OSTemplate.vmid (not template_vmid) and convert memory bytes->MB

- AttributeError: OSTemplate has no 'template_vmid' field; the actual column is 'vmid'.
- Use OSTemplate.get_vmid_for_node() to support cross-node replicated templates,
  falling back to source_node/vmid otherwise.
- VMInstance.memory is stored in bytes, but Proxmox config expects MB.

backend/tests/conftest.py

@@ -0,0 +1,92 @@
+"""
+Shared pytest fixtures.
+
+The DB engine is constructed at import time in ``app.db``. To keep tests
+hermetic we set environment variables BEFORE importing the application.
+The engine itself is created lazily-connected, so as long as no test issues
+a real query the configured URL is irrelevant.
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+import tempfile
+from pathlib import Path
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+# --- Environment must be set BEFORE importing app.* ---------------------------
+
+os.environ.setdefault("DATABASE_URL", "postgresql://test:test@localhost:5432/test")
+os.environ.setdefault("SECRET_KEY", "test-secret-key-do-not-use-in-prod")
+os.environ.setdefault("ADMIN_PASSWORD", "test-admin-password")
+os.environ.setdefault("LOG_LEVEL", "WARNING")
+
+# Generate a deterministic Fernet key for tests so encrypt/decrypt are stable.
+from cryptography.fernet import Fernet  # noqa: E402
+
+os.environ.setdefault("FERNET_KEY", Fernet.generate_key().decode())
+
+# Ensure the backend root is on sys.path so ``import app`` works regardless of
+# the working directory pytest is launched from.
+BACKEND_ROOT = Path(__file__).resolve().parent.parent
+if str(BACKEND_ROOT) not in sys.path:
+    sys.path.insert(0, str(BACKEND_ROOT))
+
+# pydantic-settings auto-loads ``.env`` from the current working directory.
+# A developer .env may contain operational keys (POSTGRES_PASSWORD, ALLOWED_HOSTS,
+# ...) that are not declared on the Settings model and would raise
+# ``extra_forbidden``. Run from a clean temp dir so only env vars are honoured.
+_TEST_CWD = Path(tempfile.mkdtemp(prefix="pvemanager-tests-"))
+os.chdir(_TEST_CWD)
+
+import pytest  # noqa: E402
+
+
+# --- Reusable fixtures --------------------------------------------------------
+
+
+@pytest.fixture
+def fake_role_factory():
+    """Build a stand-in Role object with a permissions dict."""
+
+    def _make(permissions: dict | None = None, name: str = "tester"):
+        return SimpleNamespace(
+            name=name,
+            permissions=permissions or {},
+            has_permission=lambda perm: bool((permissions or {}).get(perm)),
+        )
+
+    return _make
+
+
+@pytest.fixture
+def fake_user_factory(fake_role_factory):
+    """Build a stand-in User object compatible with auth/rbac code paths."""
+
+    def _make(
+        username: str = "alice",
+        is_admin: bool = False,
+        is_active: bool = True,
+        role=None,
+        permissions: dict | None = None,
+    ):
+        if role is None and permissions is not None:
+            role = fake_role_factory(permissions=permissions)
+        return SimpleNamespace(
+            id=1,
+            username=username,
+            is_admin=is_admin,
+            is_active=is_active,
+            role=role,
+            locked_until=None,
+        )
+
+    return _make
+
+
+@pytest.fixture
+def mock_db():
+    """Bare MagicMock standing in for a SQLAlchemy session."""
+    return MagicMock(name="db_session")