PDF Text editor (#4724)

## Summary
- add a `PdfJsonConversionService` that serializes PDF text, fonts, and
metadata to JSON and rebuilds a PDF from the same structure
- expose REST endpoints for `/pdf/json` and `/json/pdf` conversions
using the existing convert API infrastructure
- define JSON model classes capturing document metadata, font
information, and positioned text elements

## Testing
- `./gradlew spotlessApply` *(fails: plugin
org.springframework.boot:3.5.4 unavailable in build environment)*
- `./gradlew build` *(fails: plugin org.springframework.boot:3.5.4
unavailable in build environment)*

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https://chatgpt.com/codex/tasks/task_b_68f8e98d94ac8328a0e499e541528b6f

---------

Co-authored-by: EthanHealy01 <[email protected]>

.gitignore

@@ -33,6 +33,7 @@ SwaggerDoc.json
 
 # Gradle
 .gradle
+.gradle-home
 .lock
 
 # External tool builders
@@ -213,3 +214,17 @@ node_modules/
 test_batch.json
 *.backup.*.json
 frontend/public/locales/*/translation.backup*.json
+
+# Development/build artifacts
+.gradle-cache/
+scripts/pdf-collection/
+**/tmp/
+*.backup
+
+# Type3 development data
+docs/type3/signatures/
+
+
+# Type3 sample PDFs (development only)
+**/type3/samples/
+