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- Remove outdated dependencies and update dependency versions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

diff/get_patch.rs

@@ -3,6 +3,8 @@ use crate::error::{GitError, GitResult};
 use crate::pb::{GetPatchRequest, GetPatchResponse};
 use crate::resolve_revision;
 
+const MAX_PATCH_BYTES: usize = 64 * 1024 * 1024;
+
 impl GitBare {
     pub fn get_patch(&self, request: GetPatchRequest) -> GitResult<Vec<GetPatchResponse>> {
         let base = resolve_revision!(request.base);
@@ -28,6 +30,11 @@ impl GitBare {
                 stderr: String::from_utf8_lossy(&result.stderr).into_owned(),
             });
         }
+        if result.stdout.len() > MAX_PATCH_BYTES {
+            return Err(GitError::InvalidArgument(format!(
+                "patch output too large (max {MAX_PATCH_BYTES} bytes)"
+            )));
+        }
         Ok(vec![GetPatchResponse {
             data: result.stdout,
         }])