Add self-update command and fix hash mismatch after pull

- kisync update: show available releases from Gitea
- kisync update --apply: download and replace exe in-place
- Background update check after every command (non-blocking)
- Fix: compute hash from disk-read object (not server object) to prevent
  false "modified" status after pull due to line-ending differences

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/commands/pull.ts

@@ -252,7 +252,10 @@ export async function pullCommand(force = false): Promise<void> {
 
     writeEndpointToDisk(ep, endpointDir);
 
-    const hash = computeEndpointHash(ep);
+    // Хеш считаем от того, что реально записалось на диск,
+    // чтобы он совпадал при последующем readEndpointFromDisk в status
+    const diskEp = readEndpointFromDisk(endpointDir);
+    const hash = computeEndpointHash(diskEp || ep);
     newState.endpoints[ep.id] = {
       updated_at: ep.updated_at,
       folder_path: path.relative(root, endpointDir),