fix: 复合主键表改为单字段 id 以支持 ent 完整生成

desc/sql/community/post_likes.sql

@@ -1,11 +1,11 @@
 CREATE TABLE post_likes
 (
+    id         BIGINT PRIMARY KEY,
     post_id    BIGINT      NOT NULL,
     user_id    BIGINT      NOT NULL,
     created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
 
-    -- 复合主键，防止重复点赞
-    PRIMARY KEY (post_id, user_id)
+    UNIQUE (post_id, user_id)
 );
 
 -- [核心索引] 优化 "feed流中判断我是否已赞" (user_id = ? AND post_id IN (...))