refactor: update dependencies and remove unused code

- Added new dependencies: `adler2`, `crc32fast`, `flate2`, `miniz_oxide`, and `libredox`.
- Updated existing dependencies: `tokio-rustls` to version 0.26.4 and `filetime` to version 0.2.27.
- Removed the `backup.rs` file as it is no longer needed.
- Introduced tests for configuration and credential management.
- Enhanced the `identity` module to generate W3C compliant DID documents.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/adr/003-nostr-for-discovery.md

@@ -0,0 +1,35 @@
+# ADR-003: Nostr Relays for Node and App Discovery
+
+**Status**: Accepted
+**Date**: 2026-03
+
+## Context
+
+Archipelago nodes need to discover peers and community apps without a central registry. Options: custom P2P protocol, DHT, BitTorrent tracker, Nostr relays, IPFS.
+
+## Decision
+
+Use Nostr relays (NIP-78, kind 30078) for both node discovery and marketplace app manifests.
+
+## Consequences
+
+### Positive
+- **Decentralized**: Multiple independent relays; no single point of failure
+- **Existing infrastructure**: Thousands of Nostr relays already running globally
+- **Censorship-resistant**: If one relay censors, others still serve events
+- **Simple protocol**: WebSocket + JSON — easy to implement without heavy dependencies
+- **Key management**: Nostr uses secp256k1, same curve as Bitcoin — natural fit
+- **NIP-33 replaceable events**: Latest event replaces previous — clean update model
+- **Tor-compatible**: WebSocket over Tor SOCKS proxy works natively
+
+### Negative
+- **Relay availability varies**: Some relays may be down or rate-limited
+- **No guaranteed persistence**: Relays may prune old events
+- **Spam potential**: Open publishing means anyone can publish junk manifests
+- **Latency**: Querying multiple relays adds latency to discovery
+
+### Mitigation
+- Query multiple relays in parallel; deduplicate results
+- Cache results locally with 15-minute TTL
+- Use trust scoring to rank manifests (DID verification, relay consensus, federation trust)
+- Use hashtag filtering (`archipelago-marketplace`) to narrow queries