Add Gitea Actions CI/CD for automated Docker builds

- Add .gitea/workflows/docker.yml: builds and pushes Docker image on Git tags
  with semantic versioning (v0.1.0 → tags 0.1.0, 0.1, latest)
- Add .dockerignore to optimize Docker build context
- Document release process in docs/DEVELOPMENT.md
- Update CHANGELOG.md with v0.1.0 release and Unreleased CI/CD entry

Required Gitea secrets: REGISTRY_USERNAME, REGISTRY_PASSWORD

Co-authored-by: Junie <junie@jetbrains.com>

.dockerignore

@@ -1,9 +1,29 @@
-
+# Docker build context exclusions
 .git
+.github
+.gitea
+docs
+*.md
+!.markdownlint.yaml
 .idea
-**/.idea
-**/node_modules
-
-**/dist
-**/.gradle
-**/.angular
+*.iml
+node_modules
+.gradle
+build
+dist
+.DS_Store
+*.log
+*.tmp
+*.swp
+*~
+# Frontend build artifacts (built inside Docker)
+frontend/dist
+frontend/.angular
+# Backend build artifacts (built inside Docker)
+backend/build
+backend/libs
+# Test reports
+backend/build/reports
+# Secrets
+.env
+.env.*