The 'Date Range' option in Export Global Settings -> File Naming Mode
was not taking effect because fileNamingMode was missing from the
frontend ExportOptions type, default options, config loading, and
the settings-change propagation callback.
- types.ts: add fileNamingMode field to ExportOptions interface
- constants.ts: add fileNamingMode default value
- useExportConfig.ts: load fileNamingMode on init, persist on update
- ExportPage.tsx: propagate fileNamingMode in handleExportDefaultsChanged
also fix incorrect format key (defaultFormat -> format)