fix(auth): school_email unique constraint + duplicate check

- Add unique constraint on school_email (migration 007)
- Register checks both Google email and school_email for duplicates
- Add find_by_school_email to PgMemberRepository
- Error messages in Korean for user-facing conflict responses

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ImTotem

alembic/versions/007_school_email_unique.py

@@ -0,0 +1,18 @@
+"""add unique constraint on school_email
+
+Revision ID: 007
+Revises: 006
+"""
+
+from alembic import op
+
+revision = "007"
+down_revision = "006"
+
+
+def upgrade() -> None:
+    op.create_unique_constraint("uq_members_school_email", "members", ["school_email"])
+
+
+def downgrade() -> None:
+    op.drop_constraint("uq_members_school_email", "members")

src/bcsd_api/auth/service.py

@@ -41,7 +41,7 @@ def register(
     settings: Settings, repo: PgMemberRepository, conn: Connection,
 ) -> tuple[str, str]:
     profile = google_auth.verify_token(google_token, settings.google_client_id)
-    _check_duplicate(profile["email"], repo)
+    _check_duplicate(profile["email"], school_email, repo)
     member_id = generate_id("M")
     row = _build_row(
         member_id, name, profile["email"],
@@ -60,9 +60,11 @@ def _issue_jwt(payload: dict, settings: Settings) -> str:
     )
 
 
-def _check_duplicate(email: str, repo: PgMemberRepository) -> None:
+def _check_duplicate(email: str, school_email: str, repo: PgMemberRepository) -> None:
     if repo.find_by_email(email):
-        raise Conflict("member already registered")
+        raise Conflict("이미 가입된 Google 계정입니다")
+    if repo.find_by_school_email(school_email):
+        raise Conflict("이미 가입된 학교 이메일입니다")
 
 
 def _now_kst() -> str:

src/bcsd_api/member/pg_repository.py

@@ -16,6 +16,14 @@ def find_by_email(self, email: str) -> dict | None:
             return None
         return row._asdict()
 
+    def find_by_school_email(self, school_email: str) -> dict | None:
+        row = self._conn.execute(
+            select(members).where(members.c.school_email == school_email),
+        ).first()
+        if not row:
+            return None
+        return row._asdict()
+
     def create(self, row: dict) -> None:
         self._conn.execute(insert(members).values(**row))
 

src/bcsd_api/tables.py

@@ -9,7 +9,7 @@
     Column("email", String, nullable=False, unique=True),
     Column("department", String),
     Column("student_id", String),
-    Column("school_email", String),
+    Column("school_email", String, unique=True),
     Column("phone", String),
     Column("status", String, nullable=False, server_default="Beginner"),
     Column("track", String),