Add tests, docs, and changelog for #920 + #932

Audit PRs #920 (printers search/filter) and #932 (print from project
  view) for regressions, i18n coverage, test gaps, and docs.

  No regressions found: existing callers of the changed signatures
  (archive_print, getLibraryFiles, filteredPrinters chain) are unaffected;
  i18n is complete in all 7 locales for both features.

  Backend tests (4 new, all passing):
  - test_list_files_by_project_id — bulk JOIN returns files across all
    linked folders, excludes unlinked ones
  - test_list_files_folder_id_takes_precedence_over_project_id — guards
    the documented precedence folder_id > project_id > include_root
  - test_add_to_queue_with_project_id — project_id is persisted on the
    queue row for later archive linkage
  - test_add_to_queue_invalid_project_id_returns_404 — regression guard
    for the validation pre-check on the queue path (mirrors the one on
    the direct-print path in library.py)

static/index.html

@@ -23,8 +23,8 @@
 
     <!-- Splash screens for iOS -->
     <link rel="apple-touch-startup-image" href="/img/android-chrome-512x512.png" />
-    <script type="module" crossorigin src="/assets/index-DlWXszIh.js"></script>
-    <link rel="stylesheet" crossorigin href="/assets/index-CihbWKPG.css">
+    <script type="module" crossorigin src="/assets/index-BpSYztnP.js"></script>
+    <link rel="stylesheet" crossorigin href="/assets/index-dE7PVwWf.css">
   </head>
   <body>
     <div id="root"></div>