feat(doctor): add fn doctor CLI + 14 functions for system management

Adds `fn doctor` read-only diagnostic command with subcommands artefacts,
services, sync, uses-functions, unused, and --json flag for agents.
Each subcommand wraps a registry function in functions/infra/.

New functions:
- artefact_doctor, services_status, pc_locations_drift,
  audit_uses_functions, find_unused_functions (Go diagnostics)
- backup_sqlite_db, rotate_backups, wait_for_http, wait_for_port,
  port_kill, tail_journal, pre_commit_hook_install (bash utilities)
- notify_telegram (Go HTTP)
- backup_all pipeline (tag launcher)

Plus prior session leftovers (scan_secrets_in_dirty, append_diary_entry,
git utilities, http_session_cookie_middleware, compile/full-git pipelines).

Fixes pc_locations_drift filepath.Join bug with absolute dir_path.
Documents fn doctor in CLAUDE.md, .claude/rules/fn_doctor.md (rule 23),
docs/architecture.md, CHANGELOG.md (2026-05-07), and diary entry.

First fn doctor uses-functions run found drift in 7/12 apps (deuda
para sincronizar app.md con imports reales).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude/rules/INDEX.md

@@ -26,3 +26,4 @@ Reglas operativas del proyecto. Cada archivo es una regla independiente.
 | 20 | [artefactos.md](artefactos.md) | Termino paraguas para apps, analysis, vaults, projects y playgrounds (todo lo que no es codigo reutilizable) |
 | 21 | [playgrounds.md](playgrounds.md) | Prototipos rapidos dentro de un artefacto padre — heredan entorno, no se indexan, no tienen repo propio |
 | 22 | [registry_first.md](registry_first.md) | Antes de escribir codigo en un artefacto: buscar en el registry, reutilizar si existe, delegar a `fn-constructor` si falta |
+| 23 | [fn_doctor.md](fn_doctor.md) | `fn doctor`: diagnostico read-only de artefactos, services, sync drift, uses_functions, unused — wrappers de funciones del registry |