build(docker): add container setup with persistent ./data volume

Add a multi-stage Dockerfile (Vue build + .NET 10 publish) and a docker-compose service exposing port 8080 with a single bind mount ./data -> /app/data for SurrealDB persistence. Include an example compose file, a .dockerignore, and document Docker usage and version 0.0.1 in the README.

.dockerignore

@@ -0,0 +1,27 @@
+# Git / IDE
+.git
+.gitignore
+.vs
+.idea
+.vscode
+*.user
+
+# .NET build artifacts
+**/bin
+**/obj
+
+# Node
+**/node_modules
+
+# Build output (budowany wewnątrz obrazu)
+client/dist
+backend/wwwroot
+
+# Local SurrealDB data — dostarczane przez wolumen ./data
+data
+backend/data
+
+# Env / docs
+.env
+.env.*
+backend/local-docs