feat: encrypted secrets vault across CLI, desktop, dashboard, and backend

Local vault (apps/cli): clean-room PRMVLT01 format — Argon2id →
XChaCha20-Poly1305, AEAD-bound header, atomic writes. vault:* / secrets:*
/ inject (primora:// refs) / agent credential broker (dummy tokens in the
child, real secret on the wire) / TTL sessions / stack:* operator group.

Project vault (backend): core.project_secrets, AES-256-GCM via the
platform encryptor. Metadata-only list, audit-logged reveal, and
secret://NAME refs resolved at job delivery — refs stored, values never.

Surfaces: dashboard Vault page (+ local-vault card under the Tauri
shell), desktop vault window via IPC to the primora binary,
secrets:* --remote CLI mode, metadata/write-only MCP tools so agents
consume secrets via secret:// refs without holding plaintext.

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

DEPLOYMENT_GUIDE.md

@@ -37,7 +37,7 @@ docker compose -f docker-compose.yml -f docker-compose.dev.yml up -d
 | `DRAGONFLY_URL` | backend → cache DSN | yes |
 | `JWT_SECRET` | signs API JWTs (`JWT_ISSUER`, `JWT_AUDIENCE`, `JWT_TTL_SECONDS` tune tokens) | yes |
 | `BETTER_AUTH_SECRET` | auth session/signing secret | yes |
-| `PRIMORA_ENCRYPTION_KEY` | AES-256 key (64 hex chars) for integration credentials + webhook secrets at rest | production |
+| `PRIMORA_ENCRYPTION_KEY` | AES-256 key (64 hex chars) for project secrets (Vault page, `secret://` job refs), integration credentials + webhook secrets at rest | production |
 | `AUTH_BASE_URL` / `BETTER_AUTH_URL` | public auth URL (`https://host/auth`) | yes |
 | `AUTH_INTERNAL_BASE_URL` | backend → auth internal URL (`http://auth:3001`) | yes |
 | `VITE_APP_URL` / `VITE_AUTH_BASE_URL` / `VITE_API_BASE_URL` | frontend public URLs — **baked into the frontend image at build time** | yes |