feat: add "Add Page Labels" tool to the application

- Introduced a new tool for adding page labels to PDF documents, allowing users to apply Roman numerals, prefixes, and custom numbering ranges.
- Created a new HTML page for the tool with a user-friendly interface for file upload and label rule configuration.
- Implemented logic for handling file uploads, processing PDF files, and applying page labels based on user-defined rules.
- Added necessary types and utility functions for managing page label styles and normalization of start values.
- Updated main application configuration to include the new tool in the navigation.
- Added tests for page label utilities to ensure correct functionality.

public/locales/en/tools.json

@@ -86,6 +86,65 @@
     "name": "Page Numbers",
     "subtitle": "Insert page numbers into your document."
   },
+  "addPageLabels": {
+    "name": "Add Page Labels",
+    "subtitle": "Apply PDF page labels with Roman numerals, prefixes, and custom starts.",
+    "uploadHint": "PDF file",
+    "howLabelsWorkTitle": "How labels work",
+    "howLabelsWorkStep1": "Leave Page Range empty to label all pages.",
+    "howLabelsWorkStep2": "Use styles like Roman numerals for front matter and decimal numbering for the main body.",
+    "howLabelsWorkStep3": "Use Prefix with Start Value 0 to create labels such as A-0, A-1, A-2.",
+    "howLabelsWorkStep4": "Enable progress when one rule uses a disjoint range such as 1-9,30-40 or odd.",
+    "labelRulesTitle": "Label Rules",
+    "addRule": "Add Rule",
+    "removeExistingLabels": "Remove existing page labels before applying these rules",
+    "cpdfNote": "This tool uses CoherentPDF in your browser. If CoherentPDF is not configured, you will be prompted to set it up in WASM Settings.",
+    "processButton": "Add Page Labels",
+    "howItWorksUploadTitle": "Upload File",
+    "howItWorksUploadDescription": "Choose the PDF you want to relabel.",
+    "howItWorksDefineTitle": "Define Rules",
+    "howItWorksDefineDescription": "Set one or more page label rules with page ranges, styles, prefixes, and starting values.",
+    "howItWorksDownloadTitle": "Download",
+    "howItWorksDownloadDescription": "Save the updated PDF with its new page labels.",
+    "relatedToolsTitle": "Related PDF Tools",
+    "faqWhatIsQuestion": "What is a page label?",
+    "faqWhatIsAnswer": "A page label is the numbering shown by PDF readers in thumbnails, page navigation, and print dialogs. It does not print new text onto the page itself.",
+    "faqMixQuestion": "Can I mix Roman numerals and normal numbers?",
+    "faqMixAnswer": "Yes. Add multiple rules, such as 1-4 with LowercaseRoman and 5-20 with DecimalArabic.",
+    "faqPrivacyQuestion": "Do my files stay private?",
+    "faqPrivacyAnswer": "Yes. The processing happens in your browser using CoherentPDF WASM. Your PDF does not leave your device.",
+    "invalidFileTitle": "Invalid File",
+    "invalidFileMessage": "Please upload a valid PDF file.",
+    "loadingPdf": "Loading PDF...",
+    "protectedPdfTitle": "Protected PDF",
+    "protectedPdfMessage": "This PDF is password-protected. Please use the Decrypt or Change Permissions tool first.",
+    "loadErrorMessage": "Failed to load PDF file. The file may be invalid, corrupted, or password-protected.",
+    "fileMeta": "{{size}} • {{count}} pages",
+    "ruleTitle": "Label Rule {{number}}",
+    "pageRangeLabel": "Page Range",
+    "pageRangePlaceholder": "All pages, or e.g. 1-4, 7, odd",
+    "labelStyleLabel": "Label Style",
+    "labelPrefixLabel": "Label Prefix",
+    "labelPrefixPlaceholder": "Optional prefix, e.g. A-",
+    "startValueLabel": "Start Value",
+    "continueNumbering": "Continue numbering across disjoint ranges",
+    "examplesNote": "Examples: 1-4 for Roman front matter, 15-20 with prefix A- and start value 0, or odd with progress enabled.",
+    "uploadFirstMessage": "Please upload a PDF file first.",
+    "applyingLabels": "Applying page labels...",
+    "invalidRangeMessage": "Rule {{number}} has an invalid page range: {{range}}",
+    "allPages": "all pages",
+    "emptyOutputMessage": "CoherentPDF produced an empty file.",
+    "successMessage": "Page labels added successfully!",
+    "processErrorMessage": "Could not add page labels.",
+    "styleOptions": {
+      "DecimalArabic": "Decimal Arabic",
+      "LowercaseRoman": "Lowercase Roman",
+      "UppercaseRoman": "Uppercase Roman",
+      "LowercaseLetters": "Lowercase Letters",
+      "UppercaseLetters": "Uppercase Letters",
+      "NoLabelPrefixOnly": "No Label Prefix Only"
+    }
+  },
   "batesNumbering": {
     "name": "Bates Numbering",
     "subtitle": "Add sequential Bates numbers across one or more PDF files."