refactor(tgbot): share numeric keypad transitions (#6211)

Co-authored-by: n0ctal <293235942+n0ctal@users.noreply.github.com>

internal/web/service/tgbot/numeric_input.go

@@ -0,0 +1,18 @@
+package tgbot
+
+// updateNumericInput applies one key from the shared inline number pad.
+// Key -2 clears the value, -1 removes the last decimal digit, and 0..9 append
+// a digit. Callers retain their own validation and keyboard labels.
+func updateNumericInput(value, key int) int {
+	switch key {
+	case -2:
+		return 0
+	case -1:
+		if value > 0 {
+			return value / 10
+		}
+		return value
+	default:
+		return value*10 + key
+	}
+}