feat: complete daemon core milestone

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

src/daemon/discovery.rs

@@ -1,3 +1,41 @@
+use anyhow::Context;
+
+use crate::adapters::Device;
+
+use super::registry::{AdapterRegistry, DeviceRegistry};
+
 /// Background discovery orchestration for supported TV platforms.
-#[derive(Debug, Clone, Default)]
-pub struct DiscoveryService;
+#[derive(Debug, Clone)]
+pub struct DiscoveryService {
+    adapters: AdapterRegistry,
+}
+
+impl DiscoveryService {
+    /// Create a discovery service over the registered adapters.
+    pub fn new(adapters: AdapterRegistry) -> Self {
+        Self { adapters }
+    }
+
+    /// Discover all supported platforms and merge them into the registry.
+    pub async fn discover_all(&self, registry: &mut DeviceRegistry) -> anyhow::Result<Vec<Device>> {
+        let mut discovered = Vec::new();
+        for platform in self.adapters.supported_platforms() {
+            let mut devices = self
+                .discover_platform(platform, registry)
+                .await
+                .with_context(|| format!("failed discovery for platform '{platform}'"))?;
+            discovered.append(&mut devices);
+        }
+        Ok(discovered)
+    }
+
+    /// Discover one platform and merge the results into the registry.
+    pub async fn discover_platform(
+        &self,
+        platform: &str,
+        registry: &mut DeviceRegistry,
+    ) -> anyhow::Result<Vec<Device>> {
+        let discovered = self.adapters.discover(platform).await?;
+        Ok(registry.merge_discovered(discovered))
+    }
+}