chore: bump version to 0.5.6 — Dewey cascade fix

- version.json 0.5.5 → 0.5.6
- README.md What's New in v0.5.6 block
- All plugin.json max_app_version → 0.5.6

v0.5.6 ships the Dewey cascade 404 fix on top of v0.5.5 (Bulk
Enrichment, Discogs plugin, CodeRabbit hardening). v0.5.5 was
unpublished before any user saw it — v0.5.6 is the first shipped
build of this cycle.

Author: fabiodalez-dev

README.md

@@ -9,7 +9,7 @@
 
 Pinakes is a self-hosted, full-featured ILS for schools, municipalities, and private collections. It focuses on automation, extensibility, and a usable public catalog without requiring a web team.
 
-[![Version](https://img.shields.io/badge/version-0.5.5-0ea5e9?style=for-the-badge)](version.json)
+[![Version](https://img.shields.io/badge/version-0.5.6-0ea5e9?style=for-the-badge)](version.json)
 [![Installer Ready](https://img.shields.io/badge/one--click_install-ready-22c55e?style=for-the-badge&logo=azurepipelines&logoColor=white)](installer)
 [![License](https://img.shields.io/badge/License-GPL--3.0-orange?style=for-the-badge)](LICENSE)
 
@@ -24,6 +24,30 @@ Pinakes is a self-hosted, full-featured ILS for schools, municipalities, and pri
 
 ---
 
+## What's New in v0.5.6
+
+### 🐛 Fix — Dewey cascade 404s on legacy deep codes
+
+Opening the admin book-edit form on any record whose `classificazione_dewey`
+is more specific than the JSON catalog (e.g. `305.42097` when
+`data/dewey/dewey_completo_it.json` ships up to `305.4` for that subtree)
+fired a chain of 404s in the browser console: `/api/dewey/children?parent_code=305.42`,
+`...=305.420`, `...=305.4209`, `...=305.42097`. No functional breakage,
+but visually alarming and a false signal during debugging.
+
+- **`DeweyApiController::getChildren`** now returns `200 []` when the
+  parent code isn't found in the JSON (leaf semantics). Empty-name
+  children are also skipped so they don't surface as blank dropdown
+  options.
+- **`book_form.php` `navigateToCode()`** breaks the cascade loop when
+  `loadLevel()` returns null — the custom-code fallback below already
+  handles rendering the untraceable code in the breadcrumb.
+- New regression test `tests/dewey-cascade-404.spec.js` seeds a book
+  with `305.42097` and asserts zero 404s + zero console errors when
+  opening the edit form in a real Chromium.
+
+v0.5.6 includes everything from v0.5.5 plus this Dewey fix.
+
 ## What's New in v0.5.5
 
 ### 📥 Bulk ISBN Enrichment (#87 follow-up)

storage/plugins/api-book-scraper/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "8.0",
   "requires_app": "0.4.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "category": "scraping",
     "priority": 3,

storage/plugins/deezer/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "8.0",
   "requires_app": "0.5.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "category": "scraping",
     "tags": [

storage/plugins/dewey-editor/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "DeweyEditorPlugin.php",
   "requires_php": "7.4",
   "requires_app": "0.4.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "settings": false,
   "metadata": {
     "category": "admin",

storage/plugins/digital-library/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "8.0",
   "requires_app": "0.4.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "category": "media",
     "priority": 10,

storage/plugins/discogs/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "8.0",
   "requires_app": "0.5.4",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "optional": true,
     "category": "scraping",

storage/plugins/goodlib/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "8.0",
   "requires_app": "0.4.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "category": "discovery",
     "priority": 10,

storage/plugins/musicbrainz/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "8.0",
   "requires_app": "0.5.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "category": "scraping",
     "tags": [

storage/plugins/open-library/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "wrapper.php",
   "requires_php": "7.4",
   "requires_app": "0.4.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "metadata": {
     "category": "scraping",
     "tags": [

storage/plugins/z39-server/plugin.json

@@ -9,7 +9,7 @@
   "main_file": "Z39ServerPlugin.php",
   "requires_php": "7.4",
   "requires_app": "0.4.0",
-  "max_app_version": "0.5.5",
+  "max_app_version": "0.5.6",
   "settings": true,
   "metadata": {
     "category": "protocol",