fix: code quality hardening — unwrap removal, unsafe forbid, Go/Raw tests (#72)

* fix: remove unwrap() from production code, improve error handling

- Replace unwrap() with proper error handling in npm, mirror, validation
- Add input validation to cargo registry (crate name + version)
- Improve expect() messages with descriptive context in metrics, rate_limit
- Remove unnecessary clone() in error.rs, docker.rs, npm.rs, dashboard_metrics
- Add #![deny(clippy::unwrap_used)] to prevent future unwrap in prod code
- Add let-else pattern for safer null checks in validation.rs

* docs: update SECURITY.md — add 0.3.x to supported versions

* security: forbid unsafe code at crate level

Add #![forbid(unsafe_code)] to both lib.rs and main.rs.
NORA has zero unsafe blocks — this prevents future additions
without removing the forbid attribute (stronger than deny).

* build: add rust-toolchain.toml, Dockerfile HEALTHCHECK

- Pin toolchain to stable with clippy + rustfmt components
- Add Docker HEALTHCHECK for standalone deployments (wget /health)

* test: add Go proxy and Raw registry integration tests

Go proxy tests: list, .info, .mod, @latest, path traversal, 404
Raw registry tests: upload/download, HEAD, 404, path traversal,
overwrite, delete, binary data (10KB)

nora-registry/src/registry/cargo_registry.rs

@@ -3,6 +3,7 @@
 
 use crate::activity_log::{ActionType, ActivityEntry};
 use crate::audit::AuditEntry;
+use crate::validation::validate_storage_key;
 use crate::AppState;
 use axum::{
     extract::{Path, State},
@@ -26,6 +27,10 @@ async fn get_metadata(
     State(state): State<Arc<AppState>>,
     Path(crate_name): Path<String>,
 ) -> Response {
+    // Validate input to prevent path traversal
+    if validate_storage_key(&crate_name).is_err() {
+        return StatusCode::BAD_REQUEST.into_response();
+    }
     let key = format!("cargo/{}/metadata.json", crate_name);
     match state.storage.get(&key).await {
         Ok(data) => (StatusCode::OK, data).into_response(),
@@ -37,6 +42,10 @@ async fn download(
     State(state): State<Arc<AppState>>,
     Path((crate_name, version)): Path<(String, String)>,
 ) -> Response {
+    // Validate inputs to prevent path traversal
+    if validate_storage_key(&crate_name).is_err() || validate_storage_key(&version).is_err() {
+        return StatusCode::BAD_REQUEST.into_response();
+    }
     let key = format!(
         "cargo/{}/{}/{}-{}.crate",
         crate_name, version, crate_name, version