Fix version and BuildTime injection

backend/Dockerfile

@@ -1,12 +1,12 @@
 # --- BUILD STAGE ---
-FROM golang:1.25.0 AS builder
+FROM golang:1.25.3 AS builder
 WORKDIR /app
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
 
 # Fontos: CGO_ENABLED=0 a statikusan linkelt binárisért, ami kompatibilis lesz az Alpine alapú futtatási környezettel.
-RUN CGO_ENABLED=0 GOOS=linux go build -a -ldflags="-s -w" -o backend .
+RUN CGO_ENABLED=0 GOOS=linux go build -a -ldflags="-s -w -X 'main.BuildTime=$(date)'" -o backend .
 
 
 # --- DEPLOY STAGE ---