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- Remove outdated dependencies and update dependency versions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

pack/receive_pack.rs

@@ -12,6 +12,8 @@ use crate::pb::ReceivePackResponse;
 
 /// Maximum time allowed for a git receive-pack process before it is killed.
 const RECEIVE_PACK_TIMEOUT: Duration = Duration::from_secs(1800); // 30 minutes
+const MAX_RECEIVE_PACKET_BYTES: usize = 16 * 1024 * 1024;
+const MAX_RECEIVE_STDERR_BYTES: u64 = 64 * 1024;
 
 impl GitBare {
     /// Receive pack data using git-receive-pack with true concurrent streaming.
@@ -85,6 +87,9 @@ impl GitBare {
                             }
                             match result {
                                 Ok(req) => {
+                                    if req.packet.len() > MAX_RECEIVE_PACKET_BYTES {
+                                        break;
+                                    }
                                     if stdin.write_all(&req.packet).await.is_err() {
                                         break;
                                     }
@@ -134,7 +139,8 @@ impl GitBare {
             let stderr_task = {
                 let tx = tx.clone();
                 async move {
-                    if let Some(mut stderr) = stderr.take() {
+                    if let Some(stderr) = stderr.take() {
+                        let mut stderr = stderr.take(MAX_RECEIVE_STDERR_BYTES);
                         let mut s = String::new();
                         if stderr.read_to_string(&mut s).await.is_ok() && !s.is_empty() {
                             let _ = tx