fix(migrations): eid 301~305 multi-statement → 1-statement/파일 분리 (301~316)

asyncpg 러너가 exec_driver_sql 을 prepared statement(extended protocol)로 처리해
multi-statement 를 거부(cannot insert multiple commands) → fastapi init_db crash.
(001 등 초기 multi-stmt 는 postgres initdb=psql simple protocol 로 적용됐던 것 — 작성자 가정 오류.)
301~305(각 2~4 stmt)를 내용 불변으로 16개 single-statement 파일(301~316)로 분리:
 eid_study_weakness(table/rule2/idx)·eid_review_set_draft(동)·eid_weekly_recap(동)
 ·approval_requests(table/idx)·eid_schedule_views(view2). 원순서·FK 의존성 보존.
프로덕션 pkm DB 대상 트랜잭션 dry-run(ROLLBACK) 16/16 무오류 통과.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

migrations/301_eid_study_weakness_table.sql

@@ -0,0 +1,16 @@
+-- 301_eid_study_weakness_table.sql — 301_eid_study_weakness.sql 분리본 (single-statement). asyncpg 러너가 prepared statement 로 처리해 multi-statement 거부 → 1 stmt/파일. 내용 불변.
+
+CREATE TABLE IF NOT EXISTS eid_study_weakness (
+    id                   BIGSERIAL   PRIMARY KEY,
+    user_id              BIGINT      NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    weaknesses           JSONB       NOT NULL,   -- [{topic_id,topic,chronic,relapsed,leech,coverage_gap,unsure,overdue,trend,tier}]
+    habit_signals        JSONB       NOT NULL,   -- {avoidance_topics,session_abandon_rate,stale_due_count,skew_topics}
+    trend_label          VARCHAR(20) NOT NULL,   -- overall 개선|정체|악화 (코드 산출)
+    sample_attempts      INTEGER     NOT NULL DEFAULT 0,
+    is_shallow_sample    BOOLEAN     NOT NULL DEFAULT false,
+    status               VARCHAR(20) NOT NULL DEFAULT 'active',  -- 'active' | 'disputed'(dispute marker)
+    supersedes_id        BIGINT      REFERENCES eid_study_weakness(id) ON DELETE SET NULL,
+    actor                VARCHAR(20) NOT NULL,   -- 스탬프(no default) = 'eid'
+    source_generated_at  TIMESTAMPTZ NOT NULL,   -- 스탬프(no default) = 집계 시점
+    created_at           TIMESTAMPTZ NOT NULL DEFAULT now()
+);