feat: ship Rust login manager and GitLab release pipeline

Replace the legacy Go implementation as the production path, quarantine the reference tree, add deterministic release packaging and version metadata, and run verification through GitLab CI.

build.rs

@@ -0,0 +1,41 @@
+use std::{env, process::Command};
+
+fn main() {
+    for variable in [
+        "LATCHD_VERSION",
+        "LATCHD_COMMIT",
+        "LATCHD_BUILD_TIME",
+        "SOURCE_DATE_EPOCH",
+    ] {
+        println!("cargo:rerun-if-env-changed={variable}");
+    }
+
+    let version = env::var("LATCHD_VERSION")
+        .ok()
+        .filter(|value| !value.is_empty())
+        .unwrap_or_else(|| env!("CARGO_PKG_VERSION").to_owned());
+    let commit = env::var("LATCHD_COMMIT")
+        .ok()
+        .filter(|value| !value.is_empty())
+        .or_else(|| git_value(["rev-parse", "--short=12", "HEAD"]))
+        .unwrap_or_else(|| "unknown".to_owned());
+    let build_time = env::var("LATCHD_BUILD_TIME")
+        .ok()
+        .filter(|value| !value.is_empty())
+        .or_else(|| env::var("SOURCE_DATE_EPOCH").ok())
+        .unwrap_or_else(|| "unknown".to_owned());
+
+    println!("cargo:rustc-env=LATCHD_VERSION={version}");
+    println!("cargo:rustc-env=LATCHD_COMMIT={commit}");
+    println!("cargo:rustc-env=LATCHD_BUILD_TIME={build_time}");
+}
+
+fn git_value<const N: usize>(arguments: [&str; N]) -> Option<String> {
+    let output = Command::new("git").args(arguments).output().ok()?;
+    if !output.status.success() {
+        return None;
+    }
+    let value = String::from_utf8(output.stdout).ok()?;
+    let value = value.trim();
+    (!value.is_empty()).then(|| value.to_owned())
+}