v2.2.4: implement auto_overtime + overtime_unit + notif_before_minutes; remove 3 dead settings

Implemented (previously UI-only with no business effect):
- auto_overtime: when OFF, prompt user on clock-out before banking
- overtime_unit: 15/30/60-min truncation choice now actually applied
- notification_before_minutes: 30-min hardcode -> user-configurable 1~120

Removed dead keys (no readers in business logic):
- auto_detect_boot, notification_enabled, annual_leave_used

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

utils/updater_client.py

@@ -77,37 +77,55 @@ def is_newer(remote: str, local: str) -> bool:
     return _parse_version(remote) > _parse_version(local)
 
 
-def check_for_update(current_version: str, timeout: int = 5) -> Optional[ReleaseInfo]:
-    """GitHub Releases API 조회. 새 버전 있으면 ReleaseInfo, 없으면 None.
+# 업데이트 체크 결과 상수 (info=None 일 때 reason 식별)
+UP_TO_DATE = 'up_to_date'
+NETWORK_ERROR = 'network_error'
+NO_RELEASE = 'no_release'      # latest 응답 자체가 없음 (404 등)
+NO_ASSET = 'no_asset'          # release는 있으나 main.exe 자산 없음
 
-    네트워크 오류 시 None 반환 (앱 시작을 막지 않음).
+
+def check_for_update(current_version: str, timeout: int = 5):
+    """Releases API 조회.
+
+    Returns:
+        (ReleaseInfo, None) — 새 버전 있음
+        (None, UP_TO_DATE) — 이미 최신
+        (None, NETWORK_ERROR) — 네트워크/타임아웃 실패
+        (None, NO_RELEASE) — 저장소 비공개/리소스 없음 (404)
+        (None, NO_ASSET) — 새 버전이지만 main.exe 자산 미첨부
     """
     try:
         req = urllib.request.Request(RELEASES_API, headers={'User-Agent': USER_AGENT})
         with urllib.request.urlopen(req, timeout=timeout) as resp:
             data = json.loads(resp.read())
-    except (urllib.error.URLError, json.JSONDecodeError, TimeoutError):
-        return None
+    except urllib.error.HTTPError as e:
+        if e.code == 404:
+            return None, NO_RELEASE
+        return None, NETWORK_ERROR
+    except (urllib.error.URLError, json.JSONDecodeError, TimeoutError, OSError):
+        return None, NETWORK_ERROR
 
     tag = data.get('tag_name', '')
-    if not tag or not is_newer(tag, current_version):
-        return None
+    if not tag:
+        return None, NO_RELEASE
+    if not is_newer(tag, current_version):
+        return None, UP_TO_DATE
 
     asset_url = None
     for asset in data.get('assets', []):
         if asset.get('name') == ASSET_NAME:
             asset_url = asset.get('browser_download_url')
             break
-
     if not asset_url:
-        return None
+        return None, NO_ASSET
 
-    return ReleaseInfo(
+    info = ReleaseInfo(
         version=tag,
         asset_url=asset_url,
         notes=data.get('body', ''),
         published_at=data.get('published_at', ''),
     )
+    return info, None
 
 
 def download_update(asset_url: str, dest_dir: Optional[Path] = None,