fix(documents): load the local PDF parser lazily so the vault routes stop crashing

The local content-extraction reader imported pdf-parse at module top level.
pdf-parse pulls in pdfjs, whose module evaluation references the browser-only
DOMMatrix global; on the server that reference throws during chunk
instantiation and takes down every route sharing the chunk — the document
list, upload, and search among them, so old and new documents alike fail to
load. Move the parser to a lazy import() inside the extraction function
(surface type kept as a type-only import). Verified under plain Node that the
lazy path still extracts a real PDF text layer, so local indexing is
unaffected.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.28.0",
+  "version": "1.28.1",
   "description": "Self-hosted personal-health-tracking PWA with Withings integration, AI insights, and doctor-report PDF export.",
   "license": "PolyForm-Noncommercial-1.0.0",
   "homepage": "https://healthlog.dev",