Add a release-notes page linked from the footer version (v0.9.6)

Reconstructed from the commit history since the first production
deployment; the initial entry is the 0.9.0 port of the legacy bash
script to Kotlin/Spring Boot.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

build.gradle.kts

@@ -11,7 +11,7 @@ plugins {
 group = "de.hoennig"
 // bump at least the patch version for every deployment, so the UI footer
 // (BuildProperties) and --version identify what is actually running
-version = "0.9.5"
+version = "0.9.6"
 
 java {
     toolchain {