feat: add HTTP API and integration coverage

Expose the daemon request surface over /v1 with Axum, reuse shared key
parsing between CLI and HTTP, and add an isolated end-to-end HTTP test
that boots a real daemon process with temp XDG paths.

Cargo.toml

@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 anyhow = "1.0"
-axum = "0.8"
+axum = { version = "0.8", features = ["multipart"] }
 chrono = { version = "0.4", features = ["serde"] }
 clap = { version = "4.5", features = ["derive"] }
 libc = "0.2"