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/004-tor-for-peer-communication.md

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+# ADR-004: Tor Hidden Services for Peer Communication
+
+**Status**: Accepted
+**Date**: 2026-03
+
+## Context
+
+Federated nodes need to communicate directly for state sync, app deployment, and peer verification. Options: direct IP, VPN tunnel, Tor hidden services, I2P.
+
+## Decision
+
+Use Tor hidden services (.onion addresses) for all inter-node communication.
+
+## Consequences
+
+### Positive
+- **NAT traversal**: Works behind any firewall or NAT without port forwarding
+- **IP privacy**: Nodes never expose their real IP addresses to each other
+- **End-to-end encryption**: Tor provides encryption without additional TLS setup
+- **Censorship resistance**: Onion routing makes traffic analysis difficult
+- **Stable addressing**: .onion addresses persist across IP changes and network migrations
+- **No central infrastructure**: No VPN server, STUN/TURN server, or relay needed
+
+### Negative
+- **Latency**: Tor adds 200-500ms per hop; 3 hops per direction = noticeable delay
+- **Bandwidth**: Tor network has limited bandwidth; not suitable for bulk data transfer
+- **Reliability**: Tor circuits can break; connections may need retry logic
+- **Setup complexity**: Requires running a Tor daemon (`archy-tor` container)
+- **Blocked networks**: Some networks block Tor; bridges can help but add complexity
+
+### Mitigation
+- Use Tor only for RPC/control plane; bulk data (container images) pulled from registries
+- Implement retry with backoff for Tor connections
+- Container `archy-tor` runs automatically with host networking for hidden service access
+- Federation sync interval (5 min) tolerates occasional connection failures