minecraft-server: move to the java25 line (4.1.0+up2026.8.2.java25)

Minecraft 26.2 requires Java 25, so the chart's default minecraft.version can
only be raised on a java25 image. appVersion becomes 2026.8.2-java25 - the same
dated upstream release the java21 line ships, so the only variables that change
are the JVM and the Minecraft version.

The chart version stays at 4.1.0: the Java lines are siblings of one chart
generation, not successors, and are told apart by the +up suffix.

The Java boundaries in the values.yaml / NOTES.txt comments are read off
Mojang's version manifest (javaVersion.majorVersion per release), not
estimated: 1.21.11 is the last release asking for Java 21, every release from
26.1 on asks for Java 25.

minecraft-server/Chart.yaml

@@ -6,15 +6,16 @@ icon: https://avatars.githubusercontent.com/u/988985
 type: application
 
 # The Java line of this chart version is chosen through appVersion, which is
-# the image tag: the chart is published once per line (java8 / java17 / java21)
-# and minecraft.version in values.yaml must match the line published here.
+# the image tag: the chart is published once per line (java8 / java17 / java21 /
+# java25) and minecraft.version in values.yaml must match the line published
+# here.
 # Since chart 2.0.0 the tag is a DATED upstream release ("<release>-java<N>")
 # instead of the rolling line tag ("java<N>"): the rolling tags are rebuilt
 # continuously, so a pod restart could pull a different image than the last one
 # without anything being recorded anywhere. The dated tags are immutable, so the
 # image is now pinned by the chart version like every other chart in this repo.
-version: 4.1.0+up2026.8.2.java21
-appVersion: "2026.8.2-java21"
+version: 4.1.0+up2026.8.2.java25
+appVersion: "2026.8.2-java25"
 
 maintainers:
   - name: jklein