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.

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "../node_modules/@tauri-apps/cli/config.schema.json",
   "productName": "SoulStream",
-  "version": "0.1.0",
+  "version": "0.1.0-alpha.1",
   "identifier": "com.soulstream.app",
   "build": {
     "beforeDevCommand": "npm run dev",