feat: redesign admin panel & profile page, optimize Dockerfile, remove rootless

- Completely redesign admin.html matching OxiCloud design system
- Create standalone profile.html page with avatar, details & password change
- Optimize Dockerfile: 3-stage build, non-root user, OCI labels, layer cache
- Add .dockerignore to reduce build context
- Remove redundant Dockerfile.rootless & rootless-compose.yml
- Redesign login language selector as compact dropdown with search
- Fix CI/CD workflows (ci.yml, docker-build.yml, docker-publish.yml)
- Update app.js to navigate to profile page instead of modal

.dockerignore

@@ -0,0 +1,32 @@
+# Build artifacts
+target/
+
+# Git
+.git/
+.gitignore
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# Docker
+Dockerfile
+Dockerfile.rootless
+docker-compose.yml
+rootless-compose.yml
+
+# Runtime data (mapped via volumes)
+storage/
+
+# Documentation
+doc/
+*.md
+LICENSE
+CODEOWNERS
+
+# Miscellaneous
+.github/
+.env
+*.bak