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)*

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

---------

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

frontend/package-lock.json

@@ -62,6 +62,7 @@
         "react": "^19.1.1",
         "react-dom": "^19.1.1",
         "react-i18next": "^15.7.3",
+        "react-rnd": "^10.5.2",
         "react-router-dom": "^7.9.1",
         "signature_pad": "^5.0.4",
         "tailwindcss": "^4.1.13",
@@ -12081,6 +12082,16 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/re-resizable": {
+      "version": "6.11.2",
+      "resolved": "https://registry.npmjs.org/re-resizable/-/re-resizable-6.11.2.tgz",
+      "integrity": "sha512-2xI2P3OHs5qw7K0Ud1aLILK6MQxW50TcO+DetD9eIV58j84TqYeHoZcL9H4GXFXXIh7afhH8mv5iUCXII7OW7A==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": "^16.13.1 || ^17.0.0 || ^18.0.0 || ^19.0.0",
+        "react-dom": "^16.13.1 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/react": {
       "version": "19.2.0",
       "resolved": "https://registry.npmjs.org/react/-/react-19.2.0.tgz",
@@ -12102,6 +12113,29 @@
         "react": "^19.2.0"
       }
     },
+    "node_modules/react-draggable": {
+      "version": "4.4.6",
+      "resolved": "https://registry.npmjs.org/react-draggable/-/react-draggable-4.4.6.tgz",
+      "integrity": "sha512-LtY5Xw1zTPqHkVmtM3X8MUOxNDOUhv/khTgBgrUvwaS064bwVvxT+q5El0uUFNx5IEPKXuRejr7UqLwBIg5pdw==",
+      "license": "MIT",
+      "dependencies": {
+        "clsx": "^1.1.1",
+        "prop-types": "^15.8.1"
+      },
+      "peerDependencies": {
+        "react": ">= 16.3.0",
+        "react-dom": ">= 16.3.0"
+      }
+    },
+    "node_modules/react-draggable/node_modules/clsx": {
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/clsx/-/clsx-1.2.1.tgz",
+      "integrity": "sha512-EcR6r5a8bj6pu3ycsa/E/cKVGuTgZJZdsyUYHOksG/UHIiKfjxzRxYJpyVBwYaQeOvghal9fcc4PidlgzugAQg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/react-dropzone": {
       "version": "14.3.8",
       "resolved": "https://registry.npmjs.org/react-dropzone/-/react-dropzone-14.3.8.tgz",
@@ -12220,6 +12254,27 @@
       "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
       "license": "0BSD"
     },
+    "node_modules/react-rnd": {
+      "version": "10.5.2",
+      "resolved": "https://registry.npmjs.org/react-rnd/-/react-rnd-10.5.2.tgz",
+      "integrity": "sha512-0Tm4x7k7pfHf2snewJA8x7Nwgt3LV+58MVEWOVsFjk51eYruFEa6Wy7BNdxt4/lH0wIRsu7Gm3KjSXY2w7YaNw==",
+      "license": "MIT",
+      "dependencies": {
+        "re-resizable": "6.11.2",
+        "react-draggable": "4.4.6",
+        "tslib": "2.6.2"
+      },
+      "peerDependencies": {
+        "react": ">=16.3.0",
+        "react-dom": ">=16.3.0"
+      }
+    },
+    "node_modules/react-rnd/node_modules/tslib": {
+      "version": "2.6.2",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.6.2.tgz",
+      "integrity": "sha512-AEYxH93jGFPn/a2iVAwW87VuUIkR1FVUKB77NwMF7nBTDkDrrT/Hpt/IrCJ0QXhW27jTBDcf5ZY7w6RiqTMw2Q==",
+      "license": "0BSD"
+    },
     "node_modules/react-router": {
       "version": "7.9.4",
       "resolved": "https://registry.npmjs.org/react-router/-/react-router-7.9.4.tgz",