USPR-13800: bump example spring-framework.version override and add verification task

Add ext['spring-framework.version'] = '7.0.8' to both example subprojects'
build.gradle to close the BOM-precedence gap where spring-dependency-management's
managed version otherwise overrides the root resolutionStrategy floor. Also add
a verifySpringExpressionVersion Gradle task, wired into `check` for every
subproject, that fails the build if org.springframework:spring-expression
resolves below 7.0.8 anywhere in the dependency graph.

Author: claude

build.gradle

@@ -124,4 +124,22 @@ subprojects {
         consoleOutput = true
         ruleSets = ["$rootDir/ruleset.xml"]
     }
+
+    tasks.register('verifySpringExpressionVersion') {
+        doLast {
+            configurations.findAll { it.canBeResolved }.each { config ->
+                config.incoming.resolutionResult.allDependencies.each { dep ->
+                    if (dep instanceof org.gradle.api.artifacts.result.ResolvedDependencyResult) {
+                        def id = dep.selected.moduleVersion
+                        if (id != null && id.group == 'org.springframework' && id.name == 'spring-expression'
+                                && id.version < '7.0.8') {
+                            throw new GradleException("org.springframework:spring-expression resolved to ${id.version} in configuration ${config.name}, but must be >= 7.0.8 (GHSA-r5w3-xv2f-j59q)")
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    tasks.named('check') { dependsOn tasks.named('verifySpringExpressionVersion') }
 }

examples/example-spring-boot-starter-web/build.gradle

@@ -10,6 +10,7 @@ ext['jackson-2-bom.version'] = '2.21.5'
 ext['logback.version'] = '1.5.34'
 ext['netty.version'] = '4.2.16.Final'
 ext['tomcat.version'] = '11.0.22'
+ext['spring-framework.version'] = '7.0.8'
 
 dependencies {
     implementation project(':examples:examples-common')

examples/example-spring-boot-starter-webflux/build.gradle

@@ -10,6 +10,7 @@ ext['jackson-2-bom.version'] = '2.21.5'
 ext['logback.version'] = '1.5.34'
 ext['netty.version'] = '4.2.16.Final'
 ext['tomcat.version'] = '11.0.22'
+ext['spring-framework.version'] = '7.0.8'
 
 dependencies {
     implementation project(':examples:examples-common')