feat: add photo album management APIs

[marinofaggiana]

Adds support for managing Nextcloud Photos albums through WebDAV.

• Introduces NKPhotoAlbum with account-scoped identity, decoded names, album metadata, and date range parsing.
• Adds APIs to list, create, rename, and delete albums, and manage their photos.
• Encodes album path components and prevents overwriting existing albums when renaming.
• Adds an async wrapper for removing photos from albums.
• Handles empty response bodies in upload and WebDAV operations.
• Preserves progress when resuming chunked uploads.
• Adds unit tests for album identity, name decoding, and date range validation.

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI (N/A)