ci: pipeline Gitea Actions build & push Docker sur push main

- Dockerfile multi-stage (build eclipse-temurin:25-jdk → runtime)
- CI : tests via actions/setup-java puis build & push vers registry Gitea
- Trigger Watchtower après push sur main
- CLAUDE.md + rules projet (.claude/rules/)
- Version build.gradle : 0.0.1-SNAPSHOT → 0.0.1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

build.gradle

@@ -5,7 +5,7 @@ plugins {
 }
 
 group = 'com.olhar'
-version = '0.0.1-SNAPSHOT'
+version = '0.0.1'
 
 java {
     toolchain {