Add Veeam Backup for Microsoft 365 collector

PowerShell script for the VB365 server, run hourly as a SYSTEM scheduled
task (Windows PowerShell 5.1 by default, -PwshPath for PowerShell 7).
One dashboard job per VB365 backup job and backup copy job.

- Sessions from Get-VBOJobSession (and Get-VBOCopyJobSession where
  available) within the lookback window; status from session Status,
  message from the session log's warning/error lines, size from
  Statistics.TransferredData ("1.5 GB" -> bytes)
- One VB365 server can protect several Microsoft 365 organizations, so
  the dashboard company is chosen per job: OrganizationTenants mapping,
  else Tenant, else the organization's name
- Next run from the job's NextRun; empty for disabled jobs
- Get-Vb365CollectorDiagnostics.ps1 dumps jobs and sessions, showing
  each DateTime's Kind (local vs UTC); installer adapted from MARS

Not yet run against a real server.

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

README.md

@@ -12,7 +12,7 @@ browser ──nginx (basic auth, TLS)──▶ /api/* ─▶│ SQLite       │
 - `public/`: static frontend (no build step). Add `?mock=1` to the URL to use built-in sample data.
 - `backend/`: FastAPI API backed by a single SQLite file.
 - `deploy/`: nginx site and systemd unit.
-- `collectors/`: scripts that report results from backup products ([Veeam B&R](collectors/veeam/README.md), [Azure Backup / MARS](collectors/mars/README.md), [Windows Server Backup](collectors/wsb/README.md)).
+- `collectors/`: scripts that report results from backup products ([Veeam B&R](collectors/veeam/README.md), [Azure Backup / MARS](collectors/mars/README.md), [Windows Server Backup](collectors/wsb/README.md), [Veeam Backup for M365](collectors/vb365/README.md)).
 
 ## Data model