docs: unify REDIS_TTL_SECONDS env var name in design and plan

docs/superpowers/plans/2026-07-04-storage-cache-refactor.md

@@ -65,7 +65,7 @@ base-ref: 8b5e43f4915cef786208a8132460f87b8b191765
   REDIS_PORT = int(os.getenv("REDIS_PORT", "6379"))
   REDIS_DB = int(os.getenv("REDIS_DB", "0"))
   REDIS_PASSWORD = os.getenv("REDIS_PASSWORD", "")
-  REDIS_TTL_SECONDS = int(os.getenv("REDIS_TTL", "2592000"))  # 30 天
+  REDIS_TTL_SECONDS = int(os.getenv("REDIS_TTL_SECONDS", "2592000"))  # 30 天
 
   # MySQL 配置
   MYSQL_HOST = os.getenv("MYSQL_HOST", "localhost")

docs/superpowers/specs/2026-07-04-storage-cache-refactor-design.md

@@ -276,7 +276,7 @@ REDIS_HOST = os.getenv("REDIS_HOST", "localhost")
 REDIS_PORT = int(os.getenv("REDIS_PORT", "6379"))
 REDIS_DB = int(os.getenv("REDIS_DB", "0"))
 REDIS_PASSWORD = os.getenv("REDIS_PASSWORD", "")
-REDIS_TTL_SECONDS = int(os.getenv("REDIS_TTL", "2592000"))  # 30 天
+REDIS_TTL_SECONDS = int(os.getenv("REDIS_TTL_SECONDS", "2592000"))  # 30 天
 
 # MySQL 配置
 MYSQL_HOST = os.getenv("MYSQL_HOST", "localhost")