fix: replace pdf-parse with direct pdfjs-dist to fix DOMMatrix error in production

pdf-parse v2 depends on @napi-rs/canvas (native module) which fails in
Next.js standalone Docker builds — native binaries aren't traced/copied
to the standalone output, causing DOMMatrix is not defined at runtime.

Replaced pdf-parse entirely with pdfjs-dist legacy build which works
natively in Node.js without canvas or DOM API dependencies:

- New src/lib/pdf.ts: extractTextFromPdf() using pdfjs-dist/legacy/build
- Worker file explicitly imported so Next.js file tracer includes it
- Updated all call sites: documents, norms/parse, contracts
- Removed pdf-parse from dependencies, added pdfjs-dist directly
- Changed serverExternalPackages from pdf-parse to pdfjs-dist

Verified: build succeeds, both pdf.mjs and pdf.worker.mjs present in
.next/standalone, text extraction works in standalone context.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

package-lock.json

@@ -17,7 +17,7 @@
         "mammoth": "^1.12.0",
         "next": "16.2.3",
         "next-auth": "^4.24.13",
-        "pdf-parse": "^2.4.5",
+        "pdfjs-dist": "^5.4.296",
         "pg": "^8.20.0",
         "react": "19.2.4",
         "react-dom": "19.2.4"
@@ -2058,6 +2058,7 @@
       "resolved": "https://registry.npmjs.org/@napi-rs/canvas/-/canvas-0.1.80.tgz",
       "integrity": "sha512-DxuT1ClnIPts1kQx8FBmkk4BQDTfI5kIzywAaMjQSXfNnra5UFU9PwurXrl+Je3bJ6BGsp/zmshVVFbCmyI+ww==",
       "license": "MIT",
+      "optional": true,
       "workspaces": [
         "e2e/*"
       ],
@@ -7148,26 +7149,6 @@
       "dev": true,
       "license": "MIT"
     },
-    "node_modules/pdf-parse": {
-      "version": "2.4.5",
-      "resolved": "https://registry.npmjs.org/pdf-parse/-/pdf-parse-2.4.5.tgz",
-      "integrity": "sha512-mHU89HGh7v+4u2ubfnevJ03lmPgQ5WU4CxAVmTSh/sxVTEDYd1er/dKS/A6vg77NX47KTEoihq8jZBLr8Cxuwg==",
-      "license": "Apache-2.0",
-      "dependencies": {
-        "@napi-rs/canvas": "0.1.80",
-        "pdfjs-dist": "5.4.296"
-      },
-      "bin": {
-        "pdf-parse": "bin/cli.mjs"
-      },
-      "engines": {
-        "node": ">=20.16.0 <21 || >=22.3.0"
-      },
-      "funding": {
-        "type": "github",
-        "url": "https://github.com/sponsors/mehmet-kozan"
-      }
-    },
     "node_modules/pdfjs-dist": {
       "version": "5.4.296",
       "resolved": "https://registry.npmjs.org/pdfjs-dist/-/pdfjs-dist-5.4.296.tgz",