feat: complete daemon core milestone

Finish Milestone 3 with persisted config, socket IPC, registry CRUD,
periodic discovery, manual add, and app-cache refresh support.

Cargo.toml

@@ -8,6 +8,7 @@ anyhow = "1.0"
 axum = "0.8"
 chrono = { version = "0.4", features = ["serde"] }
 clap = { version = "4.5", features = ["derive"] }
+libc = "0.2"
 md5 = "0.7"
 reqwest = { version = "0.12", default-features = false, features = ["charset", "http2", "json", "multipart", "rustls-tls"] }
 roxmltree = "0.20"
@@ -20,3 +21,6 @@ tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter", "fmt"] }
 urlencoding = "2.1"
 uuid = { version = "1.0", features = ["serde", "v4"] }
+
+[dev-dependencies]
+tempfile = "3.23"