fix: inline attachment detection and account-scoped export

- Treat MIME parts with Content-ID but no Content-Disposition as inline
  - Add account_ids filter to CLI export search to avoid pulling all accounts
  - Skip failed emails during export instead of aborting the entire batch

config.toml

@@ -1,2 +1,2 @@
 base_url = "http://localhost:15630"
-api_token = "WuqNC0g8yNle7CVnxcvjUwjN"
+api_token = "eErI7WN3PtKeLwWAbIfSXCP6"