feat: endpoints de mutacion y de projects

- handlers_mutations.go: POST add_app/add_analysis/add_vault/reindex
- handlers_projects.go: GET projects y project detail (apps/analysis/vaults nested)
- handlers.go + main.go: cablear nuevas rutas
- handlers_test.go: ajustes minimos
- app.md: documentar endpoints v0.2

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

main.go

@@ -24,7 +24,7 @@ func main() {
 		log.Printf("registered database: %s (%s)", entry.Alias, entry.Path)
 	}
 
-	srv := NewServer(pool)
+	srv := NewServer(pool, root)
 	mux := http.NewServeMux()
 	srv.Routes(mux)