fix: symlink guard placement, fetch_all_assets raw count, config TOCTOU (#31)

executor.py:
- Move islink check into _safe_person_dir on the raw path, before realpath
  resolves it; the previous check at the rmtree site was unreachable dead code
  because realpath already followed any symlink

immich_api.py / jobs.py:
- fetch_all_assets now returns (assets, total_raw) where total_raw is the
  item count seen before non-dict filtering; callers use it for MIN_FACE_COUNT
  guard and display so transient non-dict API items can't incorrectly skip people
- Add WARNING when pagination stops because a page had items but all were non-dict

config.py:
- Cache _data_cfg.exists() in _data_cfg_exists so the dual-config warning
  and config_file selection always read from the same stat() result; previously
  two calls created a TOCTOU window where log and code could disagree

Bump version to 0.5.7

winnow/config.py

@@ -123,14 +123,15 @@ class _Config:
         # Prefer DATA_DIR/.immich_config.json (volume-safe in Docker) and fall back
         # to the legacy CWD path so existing installations continue to work.
         _data_cfg = Path(self.DATA_DIR) / ".immich_config.json"
-        if _data_cfg.exists() and _LEGACY_CONFIG_FILE.exists():
+        _data_cfg_exists = _data_cfg.exists()
+        if _data_cfg_exists and _LEGACY_CONFIG_FILE.exists():
             logging.warning(
                 "Two config files found: %s and %s — using %s. Remove the legacy file to silence this.",
                 _data_cfg,
                 _LEGACY_CONFIG_FILE,
                 _data_cfg,
             )
-        config_file = _data_cfg if _data_cfg.exists() else _LEGACY_CONFIG_FILE
+        config_file = _data_cfg if _data_cfg_exists else _LEGACY_CONFIG_FILE
         if config_file.exists():
             try:
                 data = json.loads(config_file.read_text())