fix(docker): prevent backend crash loop caused by pdf-parse native deps

pdf-parse@2.4.5 pulls in @napi-rs/canvas (native Skia binary) which
crashes on import in Alpine containers. Moved to lazy require() so the
app starts normally and pdf-parse loads only when PDF conversion is
actually requested.
- Lazy-load pdf-parse in pdfToStatement to avoid startup crash
- Add libc6-compat, fontconfig, freetype to Alpine runner stage
- Increase npm fetch timeouts in both Dockerfiles for slow networks
- Add connectionTimeoutMillis to pg Pool for faster failure detection

backend/src/db/pool.ts

@@ -7,4 +7,5 @@ export const pool = new Pool({
   database: config.db.database,
   user: config.db.user,
   password: config.db.password,
+  connectionTimeoutMillis: 5000,
 });