refactor: make sure dist directory exists during development

Dockerfile.dev

@@ -12,9 +12,6 @@ COPY ./internal ./internal
 COPY ./main.go ./
 COPY ./air.toml ./
 
-RUN mkdir -p ./internal/assets/dist && \
-    echo "app running" > ./internal/assets/dist/index.html
-
 RUN go install github.com/air-verse/air@v1.61.7
 
 EXPOSE 3000

air.toml

@@ -2,6 +2,7 @@ root = "/tinyauth"
 tmp_dir = "tmp"
 
 [build]
+pre_cmd = ["mkdir -p internal/assets/dist", "echo 'backend running' > internal/assets/dist/index.html"]
 cmd = "go build -o ./tmp/tinyauth ."
 bin = "tmp/tinyauth"
 include_ext = ["go"]