Add full send + receive encrypted media support in desktop DM chat:
- Paperclip attach button and drag-and-drop in ChatPane (NIP-17 mode only)
- AES-GCM encryption before upload to Blossom server
- ChatMessageEncryptedFileHeaderEvent (kind 15) wrapped in GiftWrap
- sendNip17EncryptedFile() added to IAccount interface and implementations
- DesktopUploadOrchestrator.uploadEncrypted() with proper encrypted hash
- DesktopBlossomClient ByteArray upload overload for encrypted blobs
- LRU cache in EncryptedMediaService to avoid re-downloading
- Error handling: retry on failure, disable send during upload
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
nrobi144
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