fix: add musl targets for Linux installer fallback

The installer fails on systems with glibc < 2.35 (e.g. Amazon Linux
2023) because only gnu targets are built and there is no static fallback.

- Add x86_64-unknown-linux-musl and aarch64-unknown-linux-musl to the
  cargo-dist target list so the installer can fall back to statically
  linked binaries when glibc is too old.
- Switch rig-core from reqwest-tls (OpenSSL) to reqwest-rustls (pure
  Rust TLS) to avoid a system OpenSSL dependency that breaks musl builds.

Closes #1008

Cargo.toml

@@ -144,7 +144,7 @@ rand = "0.8"
 subtle = "2"  # Constant-time comparisons for token validation
 
 # Multi-provider LLM support
-rig-core = "0.30"
+rig-core = { version = "0.30", default-features = false, features = ["reqwest-rustls"] }
 
 # AWS Bedrock (native Converse API, opt-in via --features bedrock)
 aws-config = { version = "1", features = ["behavior-version-latest"], optional = true }
@@ -262,8 +262,10 @@ publish-jobs = []
 targets = [
     "aarch64-apple-darwin",
     "aarch64-unknown-linux-gnu",
+    "aarch64-unknown-linux-musl",
     "x86_64-apple-darwin",
     "x86_64-unknown-linux-gnu",
+    "x86_64-unknown-linux-musl",
     "x86_64-pc-windows-msvc",
 ]
 # The archive format to use for windows builds (defaults .zip)