security: token_ref (Proxmox + Git tokens) returned verbatim in API responses

[pparage]

Problem

token_ref (the live Proxmox API token and Git PATs) is returned verbatim in API responses, not just stored at rest.

• GET /v1/proxmox/hosts → HostOut.token_ref (the full PVEAPIToken=... secret)
• GET /v1/catalog/sources → SourceOut.token_ref (Git PAT)

Evidence

• app/schemas/v1/proxmox.py:15 — HostOut(HostIn) includes token_ref: str
• app/schemas/v1/catalog.py:13,21 — SourceOut.token_ref
• app/routes/v1/proxmox/hosts.py _row_to_out() populates token_ref from the DB row

Impact (Critical)

Any caller that can reach the backend harvests every registered Proxmox/Git credential in one GET. The exposure is amplified by the subnet-wide CORS default (separate issue) — a single LAN device can read all tokens.

Suggested fix

Drop token_ref from the *Out response models (use a separate input-only model, or Field(exclude=True) / a masked boolean like has_token). Never echo secrets in responses regardless of the at-rest fix.

Related (at-rest, distinct): #86, #75.