Repair files broken by the web-UI merge

The merge of add-backend-api into main committed unresolved conflicts
and corrupted uploads; the API could not import on main.

- backend/app/settings.py, deploy/backup-dashboard-api.service,
  collectors/veeam/README.md: remove conflict markers, restoring the
  add-backend-api versions
- backend/app/__init__.py, backend/tests/__init__.py: were 1024 null
  bytes ("source code string cannot contain null bytes"); now empty
- Remove the accidental Backup-Dashboard gitlink at the repo root and a
  duplicate collectors/veeam/MockVeeam.ps1 (identical to tests/)
- Restore the 60-minute collector interval from 17ee303, which the
  merge reverted to 15, and update the docs to match

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

backend/app/settings.py

@@ -5,12 +5,9 @@ from pathlib import Path
 # The modal shows this many days of run history; retention can never be shorter.
 HISTORY_DAYS = 30
 
-<<<<<<< HEAD
-=======
 # Shared by the systemd service (EnvironmentFile=) and manage.py, so both always use the same DB.
 DEFAULT_ENV_FILE = "/etc/backup-dashboard/backup-dashboard.env"
 
->>>>>>> add-backend-api
 
 @dataclass(frozen=True)
 class Settings:
@@ -20,13 +17,6 @@ class Settings:
     serve_static: bool = False
 
 
-<<<<<<< HEAD
-def load_settings() -> Settings:
-    return Settings(
-        db_path=Path(os.environ.get("BACKUP_DASH_DB", "backup-dashboard.db")),
-        retention_days=max(HISTORY_DAYS, int(os.environ.get("BACKUP_DASH_RETENTION_DAYS", "90"))),
-        serve_static=os.environ.get("BACKUP_DASH_SERVE_STATIC") == "1",
-=======
 def read_env_file(path: Path) -> dict[str, str]:
     """Parse simple KEY=VALUE lines (the subset systemd's EnvironmentFile accepts)."""
     values = {}
@@ -50,5 +40,4 @@ def load_settings() -> Settings:
         db_path=Path(env.get("BACKUP_DASH_DB", "backup-dashboard.db")),
         retention_days=max(HISTORY_DAYS, int(env.get("BACKUP_DASH_RETENTION_DAYS", "90"))),
         serve_static=env.get("BACKUP_DASH_SERVE_STATIC") == "1",
->>>>>>> add-backend-api
     )