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>

core/.cargo/config.toml

@@ -0,0 +1,22 @@
+# Cargo configuration for Archipelago cross-compilation
+#
+# Native builds (x86_64 on x86_64) work automatically.
+# ARM64 cross-compilation requires the aarch64-unknown-linux-gnu toolchain.
+#
+# Install the target:
+#   rustup target add aarch64-unknown-linux-gnu
+#
+# Install the cross-linker (Debian/Ubuntu):
+#   sudo apt install gcc-aarch64-linux-gnu
+#
+# Build for ARM64:
+#   cargo build --release --target aarch64-unknown-linux-gnu
+
+[target.aarch64-unknown-linux-gnu]
+linker = "aarch64-linux-gnu-gcc"
+
+# OpenSSL cross-compilation environment (set before building)
+# These are automatically set by the build scripts but documented here:
+# OPENSSL_DIR=/usr/aarch64-linux-gnu
+# PKG_CONFIG_PATH=/usr/lib/aarch64-linux-gnu/pkgconfig
+# PKG_CONFIG_ALLOW_CROSS=1