feat: implement TTR preview functionality with caching and UI integration

backend/migrations/20261005_create_match_ttr_preview_cache.sql

@@ -0,0 +1,10 @@
+CREATE TABLE IF NOT EXISTS match_ttr_preview_cache (
+  id INT AUTO_INCREMENT PRIMARY KEY,
+  match_id INT NOT NULL,
+  snapshot_date DATE NOT NULL,
+  payload JSON NOT NULL,
+  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  UNIQUE KEY uniq_match_ttr_preview_day (match_id, snapshot_date),
+  CONSTRAINT fk_match_ttr_preview_match FOREIGN KEY (match_id) REFERENCES `match`(id) ON DELETE CASCADE
+);