docs(vibe): add erp/ guidebook (Dolibarr deployment + backup/recovery + ops)

Dedicated tree-docs guidebook under vibe/guidebooks/erp/ for the lab's most
data-critical app, cross-linked from the applications hub (bidirectional):

- README.md             : Dolibarr 22.0.4 on Postgres; data-criticality; overview
  diagram; the Vault-unseal-before-scale recovery ordering (CAUTION).
- deployment.md         : upstream image + custom entrypoint (MySQL->psql), the
  50Gi Longhorn RWX documents PVC, Vault CRDs + the shared app_roles iac, init
  scripts (conf.php creds, table-ownership), ingress, CI.
- backup-and-recovery.md: the Ansible CronJob pg_dump (daily 04:00, 15-day
  retention) + restore Job (scale-0 -> restore -> scale-1); the cluster recovery
  ordering (Longhorn -> Vault unseal -> erp scale-up).
- operations.md         : the read-only bin/arcodange CLI, static/company.json,
  Deno+Playwright tests, day-2 ops.

erp code via full gitea URLs; CLUSTER_RECOVERY.md by name; 2 mermaid diagrams
MCP-validated; zero dead links.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vibe/guidebooks/applications/README.md

@@ -10,7 +10,7 @@
 
 This guidebook maps the **deployed applications** — the workloads ArgoCD runs in their own `<app>` namespace — and, more importantly, the **single repeatable pattern** every one of them follows. Once you know the pattern, every app reads as a variation on the same skeleton: a Gitea repo whose contents (Dockerfile + Helm chart + optional Vault IaC + CI) and whose `<app>` name fully determine how it builds, deploys, gets its secrets, and is reached from the network.
 
-Two apps are presented in depth as the canonical archetypes: [webapp](webapp.md) (Go + external Postgres) and [url-shortener](url-shortener.md) (Rust + embedded SQLite). Other apps in the cluster — `erp`, `dance-lessons-coach`, `telegram-gateway`, `plausible` — instantiate the same pattern; `erp` has its own guidebook (forthcoming) and is not linked here yet.
+Two apps are presented in depth as the canonical archetypes: [webapp](webapp.md) (Go + external Postgres) and [url-shortener](url-shortener.md) (Rust + embedded SQLite). Other apps in the cluster — `erp`, `dance-lessons-coach`, `telegram-gateway`, `plausible` — instantiate the same pattern; `erp` has its own [ERP guidebook](../erp/README.md) because it carries far more moving parts than the two archetypes.
 
 ## The common app pattern
 
@@ -102,7 +102,7 @@ flowchart LR
 | [webapp](webapp.md) | Canonical **Go + external Postgres** exemplar — `iac/` + Vault dynamic creds, scalable stateless pods | ✅ Active |
 | [url-shortener](url-shortener.md) | **Rust + embedded SQLite** counterpart — single replica on a Longhorn RWO PVC, no Vault | ✅ Active |
 
-`erp` and the other apps (`dance-lessons-coach`, `telegram-gateway`, `plausible`) follow the same pattern; `erp` will be cross-linked here once its dedicated guidebook ships.
+`erp` and the other apps (`dance-lessons-coach`, `telegram-gateway`, `plausible`) follow the same pattern; `erp` is documented in depth in its own [ERP guidebook](../erp/README.md).
 
 ## Maintenance rule