feat: Implement SSH Agent Connector and gRPC server

- Added `AgentConnectorTrait` and `AgentConnector` for managing agent connections.
- Introduced `SshAgentConnector` to handle SSH-related functionalities and start a gRPC server.
- Created database entities for `agents`, `certificates`, `organizations`, `public_key_revocations`, `setup_tokens`, `upstreams`, `users`, `virtual_hosts`, and `workspaces` using SeaORM.
- Developed `CertificateService` for managing certificate generation and retrieval.
- Implemented the main server logic to initialize the database connection and start the agent server.
- Configured development settings in `development.toml` for server and database connections.

config/master/development.toml

@@ -0,0 +1,31 @@
+[server]
+bind_address = "0.0.0.0"
+port = 8080
+[server.certificate]
+san_dns = ["localhost"]
+san_ip = ["127.0.0.1"]
+
+[log]
+level = "debug"
+
+[database]
+url = "postgres://postgres:postgres@postgres:5432/nxmesh"
+max_connections = 10
+
+[grpc]
+bind_address = "0.0.0.0"
+port = 8443
+[grpc.certificate]
+san_dns = ["localhost"]
+san_ip = ["127.0.0.1"]
+
+[auth]
+jwt_secret = "development-secret-do-not-use-in-production"
+jwt_expiration_hours = 24
+
+[agent]
+name = "development-agent"
+data_dir = "./agent-runtime-data"
+
+[master]
+url = "http://localhost:8080"