Metadata editor in bulk v2 (#1349)

* Add bulk metadata editing support

* Enable multi-file selection in Metadata Editor using getOpenFileNames()

* Disable Volume, Number, and Title fields in bulk mode

* Pre-fill Series and author fields from first selected file in bulk mode

* Show status "Editing Y files" in bulk mode

* Add progress display during bulk save ("Processing X/Y: filename")

* Disable buttons during processing

* Skip read-only CBR files with error collection

* Show error summary dialog if any files fail to save

* Keep single file metadata editing the same

* Add bulk volume editing with rich tooltip

* Add checkbox next to Volume field for enabling bulk volume editing (only in bulk mode)

* Support single number (5), range (1-10), or comma list (1, 3, 5) input formats

* Sort files alphabetically before volume assignment

* Validate that volume count matches file count

* Add rich HTML tooltip explaining the feature

* Move bulkVolumeCheck widget definition to MetaEditor.ui

* Define bulkVolumeCheck QCheckBox in MetaEditor.ui instead of creating it programmatically in KCC_gui.py

* Update tab order to include bulkVolumeCheck after volumeLine

* Add multi-directory selection for bulk metadata editing

* Shift+click on editor button now opens multi-directory selection dialog
* Multiple directories enable bulk mode with volume number assignment
* Uses Qt's built-in dialog with multi-selection enabled for native look and feel

* Fix volume input validation in bulk metadata editor

* Handle invalid range formats like "1-2-3" or "--" that previously fell through, now returns an error message

* Add explicit check for empty/malformed range parts before attempting to parse

* Add positive number validation for all input types (range, comma-list, single number) to be consistent with single file mode which uses isnumeric()

* Add explicit validation for empty volumes list after parsing

* Keep metadata editor dialog open when error occur during bulks save

* Fix CBR read-only check in bulk metadata editor

* Check all files for CBR format during load instead of during save

* Unify the CBR check for single and bulk mode

* Handle mixed metadata values in bulk editing

* In bulk mode, compare Series + Writer/Penciller/Inker/Colorist across all selected files (instead of using only the first file)

* When values differ, show “(multiple values)” placeholder for that field

* Add hover tooltip with overwrite warning and a File|Value table (or Value|Count summary when there are >20 files)

* Code comments cleanup

* Use ExtendedSelection for multi-directory file dialog

* use !=

gui/MetaEditor.ui

@@ -62,6 +62,19 @@
       <item row="1" column="1">
        <widget class="QLineEdit" name="volumeLine"/>
       </item>
+      <item row="1" column="2">
+       <widget class="QCheckBox" name="bulkVolumeCheck">
+        <property name="visible">
+         <bool>false</bool>
+        </property>
+        <property name="toolTip">
+         <string>&lt;b&gt;Bulk Volume Editing&lt;/b&gt;&lt;br&gt;Check this box to assign volume numbers to multiple files.&lt;br&gt;&lt;br&gt;&lt;b&gt;Input formats:&lt;/b&gt;&lt;br&gt;&lt;code&gt;5&lt;/code&gt; → sequence starting from 5 (5, 6, 7...)&lt;br&gt;&lt;code&gt;1-10&lt;/code&gt; → range from 1 to 10&lt;br&gt;&lt;code&gt;1, 3, 5&lt;/code&gt; → specific values&lt;br&gt;&lt;br&gt;&lt;i&gt;Note: Files are sorted alphabetically before assignment.&lt;/i&gt;</string>
+        </property>
+        <property name="text">
+         <string/>
+        </property>
+       </widget>
+      </item>
       <item row="3" column="0">
        <widget class="QLabel" name="label_3">
         <property name="text">
@@ -195,6 +208,7 @@
  <tabstops>
   <tabstop>seriesLine</tabstop>
   <tabstop>volumeLine</tabstop>
+  <tabstop>bulkVolumeCheck</tabstop>
   <tabstop>titleLine</tabstop>
   <tabstop>numberLine</tabstop>
   <tabstop>writerLine</tabstop>