chore: ignore dev-note artifacts, start alpha versioning at 0.1.0-alpha.1

.gitignore now excludes everything that is not part of the app itself:
memory/, research/, TODO-Feature-Docs/, HANDOFF*/GAMEPLAN notes, .codex/,
.claude/ and logs. Version begins the alpha line at 0.1.0-alpha.1 across
the cargo workspace, package.json and tauri.conf.json.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "soulstream",
-  "version": "0.1.0",
+  "version": "0.1.0-alpha.1",
   "type": "module",
   "description": "SoulStream \u2014 music player, downloader and streamer for the Soulseek network",
   "scripts": {