build(release): hotfix 0.21.1 — add missing POM_NAME for apertus/voxtral/llm-performance

The 0.21.0 release publish failed Sonatype Central Portal validation
with "Project name is missing" on every publication of the apertus,
voxtral, and llm-performance modules — they lacked a gradle.properties
file, so vanniktech's pom-from-gradle-properties auto-config produced
POMs without <name>. (kapertus does not apply the vanniktech plugin
and therefore does not publish — no fix needed there.)

Bumps VERSION_NAME 0.21.0 → 0.21.1 so a fresh tag can re-trigger the
release workflow.

Failed run: https://github.com/SKaiNET-developers/SKaiNET-transformers/actions/runs/25099556107

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: michalharakal

gradle.properties

@@ -1,5 +1,5 @@
 GROUP=sk.ainet.transformers
-VERSION_NAME=0.21.0
+VERSION_NAME=0.21.1
 
 POM_DESCRIPTION=SKaiNET-transformers
 

llm-inference/apertus/gradle.properties

@@ -0,0 +1,2 @@
+POM_ARTIFACT_ID=skainet-transformers-inference-apertus
+POM_NAME=skainet apertus model loader

llm-inference/voxtral/gradle.properties

@@ -0,0 +1,2 @@
+POM_ARTIFACT_ID=skainet-transformers-inference-voxtral
+POM_NAME=skainet voxtral model loader

llm-performance/gradle.properties

@@ -0,0 +1,2 @@
+POM_ARTIFACT_ID=skainet-transformers-performance
+POM_NAME=skainet-transformers performance benchmarks