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- Remove outdated dependencies and update dependency versions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

oid.rs

@@ -34,10 +34,12 @@ pub fn hex_to_bytes(hex: &str) -> Result<Vec<u8>, crate::error::GitError> {
         ));
     }
 
-    (0..hex.len())
-        .step_by(2)
-        .map(|idx| {
-            u8::from_str_radix(&hex[idx..idx + 2], 16)
+    hex.as_bytes()
+        .chunks_exact(2)
+        .map(|pair| {
+            let part = std::str::from_utf8(pair)
+                .map_err(|e| crate::error::GitError::InvalidOid(e.to_string()))?;
+            u8::from_str_radix(part, 16)
                 .map_err(|e| crate::error::GitError::InvalidOid(e.to_string()))
         })
         .collect()