Implement redirection before loading content into webview

[Rylern]

The Javadoc viewer is not working when started from a package created with jpackage:

#
#  SIGSEGV (0xb) at pc=0x000000010710ea00, pid=16704, tid=259
#
# JRE version: OpenJDK Runtime Environment Temurin-25+36 (25.0+36) (build 25+36-LTS)
# Java VM: OpenJDK 64-Bit Server VM Temurin-25+36 (25+36-LTS, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, bsd-aarch64)
# Problematic frame:
# V  [libjvm.dylib+0x56ea00]  jni_CallStaticObjectMethodV+0xcc
#
# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# If you would like to submit a bug report, please visit:
#   https://github.com/adoptium/adoptium-support/issues
#

---------------  S U M M A R Y ------------

Command Line: -Djpackage.app-version=1 -XX:MaxRAMPercentage=50 --add-opens=javafx.graphics/com.sun.javafx.css=ALL-UNNAMED --enable-native-access=javafx.graphics,javafx.media,javafx.web --enable-native-access=ALL-UNNAMED --add-opens=javafx.base/com.sun.javafx.event=ALL-UNNAMED -Djpackage.app-path=/Users/pbankhea/Documents/GitHub/petebankhead/qupath/build/dist/QuPath-0.7.0-SNAPSHOT-arm64.app/Contents/MacOS/QuPath-0.7.0-SNAPSHOT-arm64 qupath.QuPath

Host: "MacBookPro17,1" arm64, 8 cores, 16G, Darwin 25.2.0, macOS 26.2 (25C56)
Time: Tue Jan 20 09:45:02 2026 GMT elapsed time: 11.203201 seconds (0d 0h 0m 11s)

This is due to the following line:

webView.getEngine().documentProperty().addListener((p, o, n) -> {});

This line was implementing redirection after a page is loaded in the web view. This PR removes this line and implement the redirection before the page is loaded in the web view.

[petebankhead]

Looks good to me, I confirm this resolves the problem on macOS.