fix(migrations): 143 asyncpg multi-statement 분리

asyncpg prepared statement 는 single-command 만 지원 (core/database.py
exec_driver_sql 경로). §1 의 143_category.sql 이 4 statement (TYPE +
ALTER + INDEX×2) 였어서 fastapi 부팅 시 asyncpg.PostgresSyntaxError
"cannot insert multiple commands into a prepared statement" 로 실패
→ 컨테이너 restart 루프.

143 을 4 개 파일로 분리:
  143: CREATE TYPE doc_category
  144: ALTER TABLE documents ADD category / ai_suggestion
  145: CREATE INDEX idx_documents_category
  146: CREATE INDEX idx_documents_has_suggestion (partial)

DB 상태는 깨끗 (migration 143 이 부분 적용 안 됨 — asyncpg 가 batch
자체를 reject). schema_migrations 에 143 도 미기록이라 재실행 안전.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

migrations/143_category.sql

@@ -1,30 +1,18 @@
 -- 143_category.sql
--- Document Server 통합 플랫폼 Section 1: category enum + ai_suggestion
+-- Document Server 통합 플랫폼 Section 1: doc_category enum 정의 (1/4)
 -- plan: luminous-sprouting-hamster.md §1
 --
--- doc_category enum (6 활성 + 3 유보):
---   document / library / news / memo / audio / video
---   mail / calendar / plex (유보)
+-- asyncpg prepared statement 는 single-command 만 허용.
+-- 원래 한 파일이던 §1 스키마 변경을 4개로 분리:
+--   143: CREATE TYPE doc_category
+--   144: ALTER TABLE documents ADD category / ai_suggestion
+--   145: CREATE INDEX idx_documents_category
+--   146: CREATE INDEX idx_documents_has_suggestion
 --
--- ai_suggestion (JSONB): 승인 전 제안 payload
---   {
---     proposed_category, proposed_path, proposed_doctype,
---     confidence, source_updated_at, reason
---   }
--- 자동 전이 금지 — /accept-suggestion 승인 시에만 category / user_tags 변경
+-- 6 활성: document / library / news / memo / audio / video
+-- 3 유보: mail / calendar / plex
 
 CREATE TYPE doc_category AS ENUM (
   'document', 'library', 'news', 'memo', 'audio', 'video',
   'mail', 'calendar', 'plex'
 );
-
-ALTER TABLE documents
-  ADD COLUMN IF NOT EXISTS category       doc_category,
-  ADD COLUMN IF NOT EXISTS ai_suggestion  JSONB;
-
-CREATE INDEX IF NOT EXISTS idx_documents_category
-  ON documents(category);
-
-CREATE INDEX IF NOT EXISTS idx_documents_has_suggestion
-  ON documents(id)
-  WHERE ai_suggestion IS NOT NULL;

migrations/144_documents_category_columns.sql

@@ -0,0 +1,14 @@
+-- 144_documents_category_columns.sql
+-- Section 1: documents 에 category / ai_suggestion 컬럼 추가 (2/4)
+-- plan: luminous-sprouting-hamster.md §1
+--
+-- ai_suggestion 구조:
+--   {
+--     proposed_category, proposed_path, proposed_doctype,
+--     confidence, source_updated_at, reason
+--   }
+-- 자동 전이 금지 — /accept-suggestion 승인 시에만 category / user_tags 변경
+
+ALTER TABLE documents
+  ADD COLUMN IF NOT EXISTS category       doc_category,
+  ADD COLUMN IF NOT EXISTS ai_suggestion  JSONB;

migrations/145_documents_category_idx.sql

@@ -0,0 +1,6 @@
+-- 145_documents_category_idx.sql
+-- Section 1: category 필터 인덱스 (3/4)
+-- plan: luminous-sprouting-hamster.md §1
+
+CREATE INDEX IF NOT EXISTS idx_documents_category
+  ON documents(category);

migrations/146_documents_has_suggestion_idx.sql

@@ -0,0 +1,9 @@
+-- 146_documents_has_suggestion_idx.sql
+-- Section 1: 승인 대기 제안 partial index (4/4)
+-- plan: luminous-sprouting-hamster.md §1
+--
+-- 승인 UI 가 hit 하는 SELECT ... WHERE ai_suggestion IS NOT NULL 용 partial idx.
+
+CREATE INDEX IF NOT EXISTS idx_documents_has_suggestion
+  ON documents(id)
+  WHERE ai_suggestion IS NOT NULL;