feat: initialize server structure and database schema

- Added initial server setup with Cargo.toml defining dependencies and project structure.
- Created build.rs for generating protobuf bindings and validating wire contracts.
- Established database schema with initial migration files for conversations, messages, and runs.
- Introduced tools and prompts for Cursor functionality, enhancing user interaction capabilities.

server/migrations/0002_llm_call_model_options.sql

@@ -0,0 +1,3 @@
+-- Persist the effective Cursor model options for each local provider call.
+ALTER TABLE llm_calls ADD COLUMN reasoning_effort TEXT;
+ALTER TABLE llm_calls ADD COLUMN fast INTEGER NOT NULL DEFAULT 0 CHECK (fast IN (0, 1));