feat: display app version in UI footer

- Add version package with build-time variables
- Inject version via ldflags in Dockerfile using git describe
- Show version in footer on every page
- Log version and commit on server startup

Dockerfile

@@ -1,6 +1,6 @@
 FROM docker.io/golang:1.25.4-alpine AS build
 
-RUN apk add --no-cache upx
+RUN apk add --no-cache upx git
 
 WORKDIR /src
 COPY go.mod go.sum ./
@@ -10,7 +10,10 @@ 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 .
+    MODULE=$(head -1 go.mod | awk '{print $2}') && \
+    VERSION=$(git describe --tags --always) && \
+    COMMIT=$(git rev-parse --short HEAD) && \
+    CGO_ENABLED=0 go build -ldflags="-s -X $MODULE/version.Version=$VERSION -X $MODULE/version.Commit=$COMMIT" -o /bin/games .
 RUN upx -9 -k /bin/games
 
 FROM scratch