Update build tooling to Java 17

The quarkus-maven-plugin 3.6.9 binary was compiled with Java 17 and
requires Java 17 to execute, even though Quarkus 3.6.9 applications
can still run on Java 11. With Maven 3.9.12 (now on GitHub Actions
ubuntu-latest runners), Java prerequisites for plugins are strictly
enforced.

This change updates the build environment to Java 17 while maintaining
Java 11 bytecode compatibility:
- GitHub Actions workflows now use Java 17
- Maven toolchains configured for Java 17
- Compiler still targets Java 11 (source=11, target=11)
- Runtime Docker image still uses Java 11

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ruhan1

.github/workflows/merge-build.yml

@@ -42,7 +42,7 @@ jobs:
       with:
         distribution: 'temurin'
         architecture: x64
-        java-version: 11
+        java-version: 17
 
     - name: maven-settings-xml-action
       uses: whelk-io/maven-settings-xml-action@v14

.github/workflows/pr-build.yml

@@ -32,7 +32,7 @@ jobs:
     - name: Set up JDK
       uses: actions/setup-java@v2
       with:
-        java-version: '11'
+        java-version: '17'
         distribution: 'adopt'
 
     - name: maven-settings-xml-action

pom.xml

@@ -254,7 +254,7 @@
                 <configuration>
                     <toolchains>
                         <jdk>
-                            <version>11</version>
+                            <version>17</version>
                             <vendor>OpenJDK</vendor>
                         </jdk>
                     </toolchains>

toolchains.xml

@@ -37,4 +37,14 @@
       <jdkHome>/usr/lib/jvm/java-11-openjdk</jdkHome>
     </configuration>
   </toolchain>
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <version>17</version>
+      <vendor>OpenJDK</vendor>
+    </provides>
+    <configuration>
+      <jdkHome>/usr/lib/jvm/java-17-openjdk</jdkHome>
+    </configuration>
+  </toolchain>
 </toolchains>