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>

bash/functions/pipelines/compile_cpp_app.md

@@ -0,0 +1,60 @@
+---
+name: compile_cpp_app
+kind: pipeline
+lang: bash
+domain: pipelines
+version: "1.0.0"
+purity: impure
+signature: "compile_cpp_app(app_name?: string) -> void"
+description: "Pipeline que resuelve la app C++ desde el nombre o CWD, la cross-compila para Windows con mingw-w64, y despliega el .exe al escritorio de Windows. Composicion de resolve_cpp_app_dir + build_cpp_windows + deploy_cpp_exe_to_windows."
+tags: [cpp, compile, windows, mingw, cross-compile, deploy, pipeline]
+uses_functions:
+  - resolve_cpp_app_dir_bash_infra
+  - build_cpp_windows_bash_infra
+  - deploy_cpp_exe_to_windows_bash_infra
+uses_types: []
+returns: []
+returns_optional: false
+error_type: "error_go_core"
+imports: []
+tested: false
+tests: []
+test_file_path: ""
+file_path: "bash/functions/pipelines/compile_cpp_app.sh"
+params:
+  - name: app_name
+    desc: "Nombre de la app a compilar (opcional). Sin arg se deduce desde el directorio actual si estamos dentro de cpp/apps/<X>/ o projects/*/apps/<X>/."
+output: "Compila el .exe y lo despliega al escritorio de Windows. Imprime progreso por steps a stderr y resumen final con ls -lh del .exe resultante."
+---
+
+## Ejemplo
+
+```bash
+# Desde dentro del directorio de la app (sin arg)
+cd /home/lucas/fn_registry/cpp/apps/chart_demo
+fn run compile_cpp_app
+
+# Con nombre explicito desde cualquier directorio
+fn run compile_cpp_app registry_dashboard
+
+# Directo
+bash bash/functions/pipelines/compile_cpp_app.sh graph_explorer
+```
+
+## Flujo
+
+1. `resolve_cpp_app_dir` — deduce nombre y directorio absoluto de la app (desde CWD o arg)
+2. Verifica que existe `CMakeLists.txt` en el directorio de la app
+3. `build_cpp_windows` — cross-compila con mingw-w64 solo el target de la app
+4. `deploy_cpp_exe_to_windows` — copia exe, DLLs, assets, enrichers y runtime al escritorio de Windows
+5. Imprime `ls -lh` del exe final en Desktop/apps/<APP>/
+
+## Variables de entorno
+
+- `FN_REGISTRY_ROOT` — raiz del registry; default `/home/lucas/fn_registry`
+- `BUILD_WIN` — directorio de build Windows; default `$FN_REGISTRY_ROOT/cpp/build/windows`
+- `WIN_DESKTOP_APPS` — directorio destino; default `/mnt/c/Users/lucas/Desktop/apps`
+
+## Notas
+
+Reemplaza la logica del slash command `/compile`. No lleva tag `launcher` porque no es un pipeline TUI-lanzable (tarda minutos en compilar).