- Add FileStore implementation for keyset persistence
- Keysets now survive server restarts
- Store keysets in JSON file at $ORLY_DATA_DIR/cashu-keysets.json
- Tokens issued before restart remain valid
Files modified:
- pkg/cashu/keyset/file_store.go: New file-based keyset store
- app/main.go: Use FileStore instead of MemoryStore
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
