feat(frontend): Upgrade embedPDF to v2.6.0 and migrate to pdf-lib fork, fix attachment/bookmark panel (#5723)

# Description of Changes

Upgrades embedPDF from v2.5.0 to v2.6.0 and migrates from unmaintained
pdf-lib to @cantoo/pdf-lib fork. Adds defensive error handling for
malformed PDFs and improves bridge lifecycle management.

### Changes

**Dependencies**
- Upgrade all @embedpdf/* packages from ^2.5.0 to ^2.6.0
- Replace pdf-lib with @cantoo/pdf-lib (maintained fork with better
TypeScript support)

**PDF Viewer Infrastructure (attachment/bookmark fix)**
- Add useDocumentReady hook to track document lifecycle across bridges
- Implement defensive bridge cleanup to prevent stale registrations
- Fix race condition in document ready state detection by subscribing to
events before checking state

**Link Extraction (updated to cantoo/pdf-lib)**
- Add graceful error handling for PDFs with invalid catalog structures
- Extract enhanced link metadata (tooltips, colors, border styles,
highlight modes)
- Return empty results instead of throwing on malformed PDFs
- Add validation for link creation (destination page bounds, rect
dimensions, color values)

**Signature Flattening  (updated to cantoo/pdf-lib)**
- Improve SVG embedding with three-tier fallback strategy (native
vector, rasterized PNG, placeholder)
- Add proper Unicode handling for PDF form tooltips via
PDFString.decodeText()
- Extract SVG utilities into cleaner strategy pattern

**Form Field Processing  (updated to cantoo/pdf-lib)**
- Add support for display labels vs export values in dropdown/list
fields per PDF spec 12.7.4.4
- Implement caching for expensive field property lookups
- Add proper handling of malformed /Opt arrays


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- What was changed
- Why the change was made
- Any challenges encountered

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---

## Checklist

### General

- [X] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [X] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [X] I have performed a self-review of my own code
- [X] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [X] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Signed-off-by: Balázs Szücs <[email protected]>

frontend/package.json

@@ -7,29 +7,29 @@
   "dependencies": {
     "@atlaskit/pragmatic-drag-and-drop": "^1.7.7",
     "@dnd-kit/core": "^6.3.1",
-    "@embedpdf/core": "^2.5.0",
-    "@embedpdf/engines": "^2.5.0",
-    "@embedpdf/models": "^2.5.0",
-    "@embedpdf/plugin-annotation": "^2.5.0",
-    "@embedpdf/plugin-attachment": "^2.5.0",
-    "@embedpdf/plugin-bookmark": "^2.5.0",
-    "@embedpdf/plugin-export": "^2.5.0",
-    "@embedpdf/plugin-history": "^2.5.0",
-    "@embedpdf/plugin-document-manager": "^2.5.0",
-    "@embedpdf/plugin-interaction-manager": "^2.5.0",
-    "@embedpdf/plugin-pan": "^2.5.0",
-    "@embedpdf/plugin-print": "^2.5.0",
-    "@embedpdf/plugin-redaction": "^2.5.0",
-    "@embedpdf/plugin-render": "^2.5.0",
-    "@embedpdf/plugin-rotate": "^2.5.0",
-    "@embedpdf/plugin-scroll": "^2.5.0",
-    "@embedpdf/plugin-search": "^2.5.0",
-    "@embedpdf/plugin-selection": "^2.5.0",
-    "@embedpdf/plugin-spread": "^2.5.0",
-    "@embedpdf/plugin-thumbnail": "^2.5.0",
-    "@embedpdf/plugin-tiling": "^2.5.0",
-    "@embedpdf/plugin-viewport": "^2.5.0",
-    "@embedpdf/plugin-zoom": "^2.5.0",
+    "@embedpdf/core": "^2.6.0",
+    "@embedpdf/engines": "^2.6.0",
+    "@embedpdf/models": "^2.6.0",
+    "@embedpdf/plugin-annotation": "^2.6.0",
+    "@embedpdf/plugin-attachment": "^2.6.0",
+    "@embedpdf/plugin-bookmark": "^2.6.0",
+    "@embedpdf/plugin-export": "^2.6.0",
+    "@embedpdf/plugin-history": "^2.6.0",
+    "@embedpdf/plugin-document-manager": "^2.6.0",
+    "@embedpdf/plugin-interaction-manager": "^2.6.0",
+    "@embedpdf/plugin-pan": "^2.6.0",
+    "@embedpdf/plugin-print": "^2.6.0",
+    "@embedpdf/plugin-redaction": "^2.6.0",
+    "@embedpdf/plugin-render": "^2.6.0",
+    "@embedpdf/plugin-rotate": "^2.6.0",
+    "@embedpdf/plugin-scroll": "^2.6.0",
+    "@embedpdf/plugin-search": "^2.6.0",
+    "@embedpdf/plugin-selection": "^2.6.0",
+    "@embedpdf/plugin-spread": "^2.6.0",
+    "@embedpdf/plugin-thumbnail": "^2.6.0",
+    "@embedpdf/plugin-tiling": "^2.6.0",
+    "@embedpdf/plugin-viewport": "^2.6.0",
+    "@embedpdf/plugin-zoom": "^2.6.0",
     "@emotion/react": "^11.14.0",
     "@emotion/styled": "^11.14.1",
     "@iconify/react": "^6.0.2",
@@ -57,7 +57,7 @@
     "i18next-browser-languagedetector": "^8.2.0",
     "jszip": "^3.10.1",
     "license-report": "^6.8.0",
-    "pdf-lib": "^1.17.1",
+    "@cantoo/pdf-lib": "^2.5.3",
     "pdfjs-dist": "^5.4.149",
     "peerjs": "^1.5.5",
     "posthog-js": "^1.268.0",