feat: add .dockerignore file and update Dockerfile to include discord-bot directory

.dockerignore

@@ -0,0 +1,15 @@
+.git
+.gitea
+.claude
+
+**/.DS_Store
+**/.env
+**/.env.*
+!**/.env.example
+
+plan.md
+README.md
+
+**/*.md
+!ha-gateway/.env.example
+!discord-bot/.env.example

ha-gateway/Dockerfile

@@ -4,6 +4,7 @@ WORKDIR /workspace
 COPY go.work go.work.sum ./
 COPY gen/ ./gen/
 COPY ha-gateway/ ./ha-gateway/
+COPY discord-bot/ ./discord-bot/
 
 WORKDIR /workspace/ha-gateway
 RUN go mod download