feat: auto-install Python deps from template pyproject.toml via uv

ExternalToolManager.discover() now accepts template root dir, detects
pyproject.toml and runs `uv sync` to create a venv. Tool invocation and
schema discovery inject the venv PATH/VIRTUAL_ENV so template tools can
import declared dependencies without manual installation.

src/llm.rs

@@ -94,7 +94,7 @@ impl LlmClient {
     pub fn new(config: &LlmConfig) -> Self {
         Self {
             client: reqwest::Client::builder()
-                .timeout(std::time::Duration::from_secs(120))
+                .timeout(std::time::Duration::from_secs(300))
                 .connect_timeout(std::time::Duration::from_secs(10))
                 .build()
                 .expect("Failed to build HTTP client"),