chore: scaffold tvctl foundation

Set up the Rust crate, baseline module layout, and project docs so the
repository matches the design bundle and builds cleanly as a starting point.

src/daemon/cache.rs

@@ -0,0 +1,10 @@
+use crate::adapters::AppInfo;
+
+/// A platform-level cache of app metadata discovered from live devices.
+#[derive(Debug, Clone, Default)]
+pub struct AppCache {
+    /// The normalized platform identifier for the cache file.
+    pub platform: String,
+    /// The apps currently known for that platform.
+    pub apps: Vec<AppInfo>,
+}