Make manage.py use the service's database

manage.py only found the database via BACKUP_DASH_DB, which is set in
the systemd unit and not in an admin's shell, so it silently created a
new backup-dashboard.db in the current directory. API keys created
there were never seen by the service.

- Settings now come from /etc/backup-dashboard/backup-dashboard.env,
  which both the systemd unit (EnvironmentFile=) and manage.py read;
  real environment variables still take precedence
- manage.py prints the database it uses and refuses to create a new
  one unless --create is passed; --db overrides the path

Co-Authored-By: Claude Opus 5.5 <[email protected]>

backend/tests/test_manage.py

@@ -0,0 +1,52 @@
+import subprocess
+import sys
+from pathlib import Path
+
+from app.settings import load_settings
+
+BACKEND = Path(__file__).resolve().parents[1]
+
+
+def run_manage(*args, env, cwd):
+    return subprocess.run([sys.executable, str(BACKEND / "manage.py"), *args],
+                          capture_output=True, text=True, env=env, cwd=cwd)
+
+
+def base_env(tmp_path, monkeypatch):
+    env_file = tmp_path / "backup-dashboard.env"
+    monkeypatch.setenv("BACKUP_DASH_ENV_FILE", str(env_file))
+    monkeypatch.delenv("BACKUP_DASH_DB", raising=False)
+    return env_file, {"BACKUP_DASH_ENV_FILE": str(env_file), "PYTHONPATH": str(BACKEND), "PATH": "/usr/bin:/bin"}
+
+
+def test_env_file_supplies_db_path_and_real_env_wins(tmp_path, monkeypatch):
+    env_file, _ = base_env(tmp_path, monkeypatch)
+    env_file.write_text('# comment\nBACKUP_DASH_DB="/srv/from-file.db"\nBACKUP_DASH_RETENTION_DAYS=120\n')
+    assert load_settings().db_path == Path("/srv/from-file.db")
+    assert load_settings().retention_days == 120
+    monkeypatch.setenv("BACKUP_DASH_DB", "/srv/from-env.db")
+    assert load_settings().db_path == Path("/srv/from-env.db")
+
+
+def test_manage_refuses_to_create_db_implicitly(tmp_path, monkeypatch):
+    _, env = base_env(tmp_path, monkeypatch)
+    workdir = tmp_path / "somewhere-else"
+    workdir.mkdir()
+    r = run_manage("create-key", "k", env=env, cwd=workdir)
+    assert r.returncode != 0
+    assert "Database not found" in r.stderr
+    assert not (workdir / "backup-dashboard.db").exists()
+
+
+def test_manage_uses_db_from_env_file(tmp_path, monkeypatch):
+    env_file, env = base_env(tmp_path, monkeypatch)
+    service_db = tmp_path / "service.db"
+    env_file.write_text(f"BACKUP_DASH_DB={service_db}\n")
+    assert run_manage("--create", "list-keys", env=env, cwd=tmp_path).returncode == 0  # service's first start
+    workdir = tmp_path / "somewhere-else"
+    workdir.mkdir()
+    r = run_manage("create-key", "veeam-acme", env=env, cwd=workdir)
+    assert r.returncode == 0, r.stderr
+    assert str(service_db) in r.stderr
+    assert "veeam-acme" in run_manage("list-keys", env=env, cwd=tmp_path).stdout
+    assert not (workdir / "backup-dashboard.db").exists()