Add Import/Export feature: JSON state backup and filesystem metadata export

[Copilot]

Adds three import/export capabilities to the Settings page: JSON backup/restore of app state, and writing enriched metadata alongside media files for persistence across rescans.

Settings UI

• New collapsible Import / Export section above Troubleshooting, matching existing style
• Three checkboxes control JSON export scope: Settings, Overrides, Matches
• Three action buttons: Export to JSON, Import from JSON, Export metadata to media folders

JSON export/import (ImportExportService)

• exportJson saves selected state slices (API keys/view options, overrides, matched TMDB/TVDB IDs + episode names) to a single smb_export_YYYY-MM-DD.json via SAF directory picker
• importJson restores via document picker; only sections present in the file are applied

Filesystem metadata export

• exportToFilesystem writes alongside each show/movie folder:
  • smb.json — versioned (smbVersion: 1) with provider IDs, metadataSource, episode titles, and user overrides
  • poster.jpg — copied from local provider cache
  • smb_thumb_s01e02.jpg — per-episode thumbnails written to their season directory

FileScanner pickup on rescan

• recursiveCollect detects smb.json and smb_thumb_*.jpg during traversal
• IDs, episode titles, and thumbnail URIs are applied in buildLibrary/buildMovieList
• API-enriched data always wins over smb.json values (smb.json acts as a fallback/seed)
• Shared smbThumbFilename() + SMB_THUMB_REGEX in SmbTypes.ts keep writer and reader in sync

[Kallb123]

@copilot There are new import references to LegacyFileSystem. Refactor these into the modern class based system.
Have look across the changes as a reviewer, there are some variables with old names.

[Copilot]

@copilot There are new import references to LegacyFileSystem. Refactor these into the modern class based system.
Have look across the changes as a reviewer, there are some variables with old names.

Done in commits b9e2e3c and dbfad88.

LegacyFileSystem removed:

• FileScanner.ts: dropped the import * as LegacyFileSystem line; the single SAF-based readAsStringAsync call (for smb.json) now goes through StorageAccessFramework which was already imported.
• ImportExportService.ts: replaced the wildcard import with import { File } from 'expo-file-system' and import { StorageAccessFramework } from 'expo-file-system/legacy' directly; all LegacyFileSystem.readAsStringAsync calls replaced with await new File(uri).text() (text) or await new File(uri).base64() (binary) using the modern class API.

Old variable names fixed:

• ShowMatchExport.seasons[*].episodes[*] field renamed from tmdbTitle → episodeTitle (provider-agnostic), with the export/import mapping updated accordingly (ep.tmdbTitle → JSON episodeTitle on export; JSON ep.episodeTitle → Redux tmdbTitle on import).

[Kallb123]

@copilot the import of StorageAccessFramework from the legacy library should be able to be updated to a modern version. I don't think we use this elsewhere for the same purpose.

[Copilot]

@copilot the import of StorageAccessFramework from the legacy library should be able to be updated to a modern version. I don't think we use this elsewhere for the same purpose.

Done in the latest commit. The expo-file-system/legacy import for StorageAccessFramework has been removed from ImportExportService.ts and replaced entirely with the modern class-based API:

• StorageAccessFramework.requestDirectoryPermissionsAsync() → Directory.pickDirectoryAsync()
• StorageAccessFramework.readDirectoryAsync() → new Directory(dirUri).list() (synchronous, returns (Directory | File)[])
• StorageAccessFramework.createFileAsync() → directory.createFile(name, mimeType) (synchronous)
• StorageAccessFramework.writeAsStringAsync() → file.write(content, { encoding }) (synchronous, accepts 'base64' encoding natively)

The writeSafBase64 helper wrapper was also removed since the modern File.write() accepts a { encoding: 'base64' } option directly. The modern Directory/File classes fully support SAF content:// URIs on Android via the SAFDocumentFile backend, confirmed from the native Kotlin source.