refactor(cache): redesign cache system with structured keys and improved performance

- Add repo_path parameter to cached_response and cached_vec_response functions
- Implement structured cache key format with namespace, repo_path, and request proto
- Replace global cache with Moka in-memory cache using weight-based eviction
- Set 256MB memory cap with 10-minute TTL and 2-minute TTI policy
- Add metrics collection for cache operations and evictions
- Implement efficient repo-scoped invalidation using key structure
- Add detailed documentation comments explaining cache architecture
- Remove outdated dependencies and update dependency versions
- Add error handling for encoding failures in cache operations
- Optimize Vec responses with length-delimited encoding and pre-allocation

tests/snapshot_test.rs

@@ -140,3 +140,17 @@ fn test_local_snapshot_storage_delete() {
     // Delete non-existent
     assert!(storage.delete_snapshot("nonexistent").is_err());
 }
+
+#[test]
+fn test_local_snapshot_storage_rejects_traversal_id() {
+    let dir = tempfile::tempdir().unwrap().path().to_path_buf();
+    let storage = LocalSnapshotStorage::new(dir);
+
+    assert!(storage.read_snapshot("../escape").is_err());
+    assert!(storage.delete_snapshot("../escape").is_err());
+    assert!(
+        storage
+            .write_snapshot("../escape", "repo.git", "abc123", b"data")
+            .is_err()
+    );
+}