HDFS-17934. RBF: Add router web address to router web UI

[kokonguyen191]

Description of PR

In router web interface, there are clickable URLs for namenodes and datanodes, but none for routers.

This patch uses a hacky method to guess the web URL from configuration and admin address, which works for cluster that runs the same port for all routers, instead of 100% accurately getting it using some other method that requires more intrusive changes to what's stored in the router state store. I think it's a fair compromise for a small improvement that works for most deployments.

How was this patch tested?

Local deployment and test deployment with a few nodes.

No unit tests since it's a minor front end change.

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 23s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 1s		codespell was not available.
+0 🆗	detsecrets	0m 1s		detect-secrets was not available.
+0 🆗	xmllint	0m 1s		xmllint was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+1 💚	mvninstall	26m 4s		trunk passed
+1 💚	compile	0m 41s		trunk passed with JDK Ubuntu-21.0.11+10-1-24.04.2-Ubuntu
+1 💚	compile	0m 52s		trunk passed with JDK Ubuntu-17.0.19+10-1-24.04.2-Ubuntu
+1 💚	checkstyle	1m 9s		trunk passed
+1 💚	mvnsite	0m 55s		trunk passed
+1 💚	javadoc	0m 57s		trunk passed with JDK Ubuntu-21.0.11+10-1-24.04.2-Ubuntu
+1 💚	javadoc	0m 41s		trunk passed with JDK Ubuntu-17.0.19+10-1-24.04.2-Ubuntu
+1 💚	spotbugs	1m 21s		trunk passed
+1 💚	shadedclient	16m 25s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 32s		the patch passed
+1 💚	compile	0m 24s		the patch passed with JDK Ubuntu-21.0.11+10-1-24.04.2-Ubuntu
+1 💚	javac	0m 24s		the patch passed
+1 💚	compile	0m 31s		the patch passed with JDK Ubuntu-17.0.19+10-1-24.04.2-Ubuntu
+1 💚	javac	0m 31s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 16s		the patch passed
+1 💚	mvnsite	0m 35s		the patch passed
+1 💚	javadoc	0m 21s		the patch passed with JDK Ubuntu-21.0.11+10-1-24.04.2-Ubuntu
+1 💚	javadoc	0m 21s		the patch passed with JDK Ubuntu-17.0.19+10-1-24.04.2-Ubuntu
+1 💚	spotbugs	1m 12s		the patch passed
+1 💚	shadedclient	15m 51s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	42m 54s		hadoop-hdfs-rbf in the patch passed.
+1 💚	asflicense	0m 25s		The patch does not generate ASF License warnings.
		114m 5s

Subsystem	Report/Notes
Docker	ClientAPI=1.54 ServerAPI=1.54 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8540/1/artifact/out/Dockerfile
GITHUB PR	#8540
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets xmllint
uname	Linux 0e03ef8879e7 5.15.0-181-generic #191-Ubuntu SMP Fri May 22 19:09:02 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / dc55daa
Default Java	Ubuntu-17.0.19+10-1-24.04.2-Ubuntu
Multi-JDK versions	/usr/lib/jvm/java-21-openjdk-amd64:Ubuntu-21.0.11+10-1-24.04.2-Ubuntu /usr/lib/jvm/java-17-openjdk-amd64:Ubuntu-17.0.19+10-1-24.04.2-Ubuntu
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8540/1/testReport/
Max. process+thread count	3034 (vs. ulimit of 10000)
modules	C: hadoop-hdfs-project/hadoop-hdfs-rbf U: hadoop-hdfs-project/hadoop-hdfs-rbf
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8540/1/console
versions	git=2.43.0 maven=3.9.15 spotbugs=4.9.7
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[ZanderXu]

Make Sense. LGTM + 1