fix(profile): apply custom avatar immediately on idle setCustomAvatar / connect

Review feedback on PR #56:

1. setCustomAvatar(buf) now triggers applyIdleAvatar when the bot is idle
   (currentSong=null OR avatarEnabled=false). Spec said this; original impl
   only stored the buffer, so a fresh upload from Settings was invisible
   until next stop event. Track currentSong in BotProfileManager for the
   idle check.

2. onConnect drops the !avatarEnabled guard — on a fresh connect there's
   no song playing yet, so the spec matrix wants the custom avatar shown
   regardless of sync. Previously bots reconnected with a stale TS3
   server-side avatar.

3. CustomAvatarRow: defer the initializing=false flip to nextTick so the
   load-time data-url assignment's queued watcher sees initializing=true
   and bails. Removes the redundant PUT-on-mount that echoed the just-
   loaded bytes back to the server.

4. BotInstance avatar load wrapped in try/catch — a corrupt/locked file
   no longer crashes startup; we log and continue with no custom avatar.

Tests rewritten: 10 cases covering the full behavior matrix
(idle vs playing × sync on/off × custom set/null × stop/connect).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/bot/instance.ts

@@ -94,10 +94,15 @@ export class BotInstance extends EventEmitter {
       options.tsOptions.nickname,
     );
 
-    const relPath = this.database.getCustomAvatarPath(this.id);
-    if (relPath) {
-      const buf = this.avatarStore.read(relPath);
-      if (buf) this.profileManager.setCustomAvatar(buf);
+    // Best-effort: a corrupted/locked avatar file must not block bot startup.
+    try {
+      const relPath = this.database.getCustomAvatarPath(this.id);
+      if (relPath) {
+        const buf = this.avatarStore.read(relPath);
+        if (buf) this.profileManager.setCustomAvatar(buf);
+      }
+    } catch (err) {
+      this.logger.warn({ err }, "Failed to load custom avatar — skipping");
     }
 
     this.setupPlayerEvents();