Xray-core: Dynamic Chrome User-Agent for all HTTP requests by default (overwriteable through config) (#5658)

https://github.com/XTLS/Xray-core/issues/4996#issuecomment-3855274627
https://github.com/XTLS/Xray-core/pull/5658#issuecomment-3857332687

---------

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>
Co-authored-by: Fangliding <63339210+Fangliding@users.noreply.github.com>

common/utils/browser.go

@@ -0,0 +1,28 @@
+package utils
+
+import (
+	"math/rand"
+	"strconv"
+	"time"
+
+	"github.com/klauspost/cpuid/v2"
+)
+
+func ChromeVersion() int {
+	// Use only CPU info as seed for PRNG
+	seed := int64(cpuid.CPU.Family + cpuid.CPU.Model + cpuid.CPU.PhysicalCores + cpuid.CPU.LogicalCores + cpuid.CPU.CacheLine)
+	rng := rand.New(rand.NewSource(seed))
+	// Start from Chrome 144 released on 2026.1.13
+	releaseDate := time.Date(2026, 1, 13, 0, 0, 0, 0, time.UTC)
+	version := 144
+	now := time.Now()
+	// Each version has random 25-45 day interval
+	for releaseDate.Before(now) {
+		releaseDate = releaseDate.AddDate(0, 0, rng.Intn(21)+25)
+		version++
+	}
+	return version - 1
+}
+
+// ChromeUA provides default browser User-Agent based on CPU-seeded PRNG.
+var ChromeUA = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/" + strconv.Itoa(ChromeVersion()) + ".0.0.0 Safari/537.36"