Show rank tier and ELO alongside RZ points in the coins badge

Adds a server-computed tier/division (Bronze..Diamond, III-I) to the
ratings profile endpoint and surfaces it next to the numeric ELO in the
shared header badge, matching the coin balance display already there.

scripts/autoload/question_bank_service.gd

@@ -38,6 +38,8 @@ var load_state := "idle"
 var retry_attempt := 0
 var next_retry_seconds := 0
 var overall_elo := 1000
+var rank_tier := "Bronze"
+var rank_division := 3
 var rated_question_count := 0
 var category_elos := {}
 var last_rating_change := {}
@@ -246,6 +248,8 @@ func clear_questions() -> void:
 	retry_attempt = 0
 	next_retry_seconds = 0
 	overall_elo = 1000
+	rank_tier = "Bronze"
+	rank_division = 3
 	rated_question_count = 0
 	category_elos = {}
 	last_rating_change = {}
@@ -617,6 +621,8 @@ func _on_ratings_loaded(result: int, response_code: int, _headers: PackedStringA
 		return
 
 	overall_elo = int(parsed.get("overallElo", parsed.get("overall_elo", 1000)))
+	rank_tier = str(parsed.get("tier", rank_tier))
+	rank_division = int(parsed.get("tierDivision", parsed.get("tier_division", rank_division)))
 	rated_question_count = int(parsed.get("ratedQuestionCount", parsed.get("rated_question_count", 0)))
 	category_elos = parsed.get("categoryElos", parsed.get("category_elos", {}))
 	ratings_changed.emit()