As a gRPC and MCP API consumer
I want to be call key/value endpoints in MCP and gRPC, like I can in REST
So that I can easily create or retrieve a key/value with MCP/gRPC

Given key_value_controller.rs already exists and interfaces with key_value_service.rs
When adding key value support to gRPC and MCP
When use key_value_controller.rs as an example of how to integrate with key_value_service.rs
And refactor key_value_service.rs to provide functions for either base64 encoded content or binary content, re-using overlapping code
And use the binary content oriented function with proto buffers (with key_value_handler.rs)

Given pointer_handler.rs already exist
When adding key_value_handler.rs
Then use pointer_handler.rs and pointer_tool.rs as examples
And integrate with key_value_service.rs
And create/use the key_value.proto as defined below:


```
syntax = "proto3";

package pointer;

service PointerService {
  rpc CreateKeyValue(CreateKeyValueRequest) returns (KeyValueResponse);
  rpc GetKeyValue(GetKeyValueRequest) returns (KeyValueResponse);
}

message CreateKeyValueRequest {
  string bucket = 1;
  string object = 2;
  bytes content = 3;
}

message GetKeyValueRequest {
  string bucket = 1;
  string object = 2;
  bytes content = 3;
}

message KeyValueResponse {
  string bucket = 1;
  string object = 2;
}
```

Given pointer_tool.rs already exist
When adding key_value_tool.rs
Then use pointer_tool.rs as examples
And integrate with key_value_service.rs

Implementation Notes

- Place any unit tests at the bottom of the same file as the associated production code
- Increment patch version of anttp package in Cargo.toml
- Create a copy of this issue description and save to /spec using the name of this issue as the filename (with lower underscore case, starting with the 5 char padded issue number, e.g. 00001_issue_title.txt)
- Update unit tests to validate the changes

Amendments

- Rename GetKeyValueBinaryResponse to GetKeyValueResponse in key_value.proto and update related code
- Update key_value_tool.rs to call get_key_value and create_key_value, rather than the binary versions. Use BASE64_STANDARD.decode and BASE64_STANDARD.encode respectively. See public_data_tool.rs as an example.