fix(db): clamp traffic counters below int64 max and repair overflowed rows

A counter pushed past int64 (multi-node setups hit this via historic
delta-compounding bugs) makes SQLite silently promote the INTEGER cell
to REAL. From then on the column no longer scans into the Go int64
field and every reader of client_traffics fails at once: the inbounds
page, xray restarts, and node traffic sync all return "converting
driver.Value type float64 to int64".

Two-part fix: every unbounded "up = up + ?" add (local traffic, node
delta merge, inbound counters, plus the Go-side outbound accumulation)
now saturates at TrafficMax, a cap safely below math.MaxInt64 so one
more delta cannot overflow; and a startup repair casts REAL-promoted
cells back to INTEGER and clamps all traffic counters into
[0, TrafficMax] across client_traffics, inbounds, outbound_traffics
and node_client_traffics, restoring access to already-corrupted panels
without manual sqlite surgery.

Closes #5762

internal/database/traffic_overflow_repair_test.go

@@ -0,0 +1,103 @@
+package database
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/mhsanaei/3x-ui/v3/internal/xray"
+)
+
+// TestRepairOverflowedTrafficCounters_HealsSQLiteRealPromotion reproduces
+// #5762: a counter pushed past int64 makes SQLite silently store the cell as
+// REAL, after which scanning the row back into the Go int64 field fails and
+// every reader of client_traffics breaks. The startup repair must convert the
+// cell back to a scannable integer clamped to TrafficMax.
+func TestRepairOverflowedTrafficCounters_HealsSQLiteRealPromotion(t *testing.T) {
+	dbDir := t.TempDir()
+	t.Setenv("XUI_DB_FOLDER", dbDir)
+	if err := InitDB(filepath.Join(dbDir, "x-ui.db")); err != nil {
+		t.Fatalf("InitDB failed: %v", err)
+	}
+	t.Cleanup(func() { _ = CloseDB() })
+
+	rows := []xray.ClientTraffic{
+		{Email: "overflowed@x", Enable: true, Up: 5, Down: 6},
+		{Email: "negative@x", Enable: true, Up: 7, Down: 8},
+		{Email: "healthy@x", Enable: true, Up: 100, Down: 200},
+	}
+	for i := range rows {
+		if err := db.Create(&rows[i]).Error; err != nil {
+			t.Fatalf("create traffic row %d: %v", i, err)
+		}
+	}
+
+	if err := db.Exec("UPDATE client_traffics SET down = 1.2247589467272907e+19 WHERE email = 'overflowed@x'").Error; err != nil {
+		t.Fatalf("corrupt down: %v", err)
+	}
+	if err := db.Exec("UPDATE client_traffics SET up = -42 WHERE email = 'negative@x'").Error; err != nil {
+		t.Fatalf("corrupt up: %v", err)
+	}
+
+	var broken []xray.ClientTraffic
+	if err := db.Find(&broken).Error; err == nil {
+		t.Fatal("expected the REAL-promoted row to break scanning before the repair")
+	}
+
+	if err := repairOverflowedTrafficCounters(); err != nil {
+		t.Fatalf("repairOverflowedTrafficCounters: %v", err)
+	}
+
+	byEmail := map[string]xray.ClientTraffic{}
+	var repaired []xray.ClientTraffic
+	if err := db.Find(&repaired).Error; err != nil {
+		t.Fatalf("scan after repair: %v", err)
+	}
+	for _, r := range repaired {
+		byEmail[r.Email] = r
+	}
+	if got := byEmail["overflowed@x"].Down; got != TrafficMax {
+		t.Errorf("overflowed down: expected clamp to %d, got %d", TrafficMax, got)
+	}
+	if got := byEmail["overflowed@x"].Up; got != 5 {
+		t.Errorf("overflowed up: expected untouched 5, got %d", got)
+	}
+	if got := byEmail["negative@x"].Up; got != 0 {
+		t.Errorf("negative up: expected clamp to 0, got %d", got)
+	}
+	if got := byEmail["healthy@x"]; got.Up != 100 || got.Down != 200 {
+		t.Errorf("healthy row changed: %+v", got)
+	}
+}
+
+// TestClampedAddExpr_CapsAtTrafficMax verifies the write-path clamp: a delta
+// applied to a counter near the cap must saturate at TrafficMax instead of
+// overflowing int64 (which SQLite would promote to REAL).
+func TestClampedAddExpr_CapsAtTrafficMax(t *testing.T) {
+	dbDir := t.TempDir()
+	t.Setenv("XUI_DB_FOLDER", dbDir)
+	if err := InitDB(filepath.Join(dbDir, "x-ui.db")); err != nil {
+		t.Fatalf("InitDB failed: %v", err)
+	}
+	t.Cleanup(func() { _ = CloseDB() })
+
+	row := xray.ClientTraffic{Email: "near-cap@x", Enable: true, Up: TrafficMax - 10, Down: 1}
+	if err := db.Create(&row).Error; err != nil {
+		t.Fatalf("create traffic row: %v", err)
+	}
+
+	query := "UPDATE client_traffics SET up = " + ClampedAddExpr("up") + ", down = " + ClampedAddExpr("down") + " WHERE email = ?"
+	if err := db.Exec(query, int64(1_000_000), int64(5), "near-cap@x").Error; err != nil {
+		t.Fatalf("clamped add: %v", err)
+	}
+
+	var got xray.ClientTraffic
+	if err := db.Where("email = ?", "near-cap@x").First(&got).Error; err != nil {
+		t.Fatalf("scan after clamped add: %v", err)
+	}
+	if got.Up != TrafficMax {
+		t.Errorf("up: expected saturation at %d, got %d", TrafficMax, got.Up)
+	}
+	if got.Down != 6 {
+		t.Errorf("down: expected 6, got %d", got.Down)
+	}
+}