fix: run templ generate in Dockerfile before build

The _templ.go files are gitignored, so the Docker build context doesn't
include them. Generate them before compiling.

Dockerfile

@@ -7,6 +7,7 @@ COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .
+RUN go tool templ generate
 RUN go tool gotailwind -i assets/css/input.css -o assets/css/output.css --minify
 RUN --mount=type=cache,target=/root/.cache/go-build \
     CGO_ENABLED=0 go build -ldflags="-s" -o /bin/games .