Refactor for TDD workflow with Vitest and ESLint

- Move API keys from hardcoded values to .env via dotenv
- Extract business logic into src/trading.ts with dependency injection
- Add typed AlpacaClient interface, replace `any` on Alpaca class
- Add Vitest test suites for trading logic and Alpaca wrapper (14 tests)
- Set up ESLint with @typescript-eslint for linting
- Fix getAsset to pass symbol string directly to SDK
- Fix typo (alpacha -> alpaca), remove unused ws/node-fetch deps
- Update .gitignore for node_modules and .env

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -1,18 +1,24 @@
 {
   "devDependencies": {
     "@types/node": "^22.13.1",
-    "@types/ws": "^8.5.14",
+    "@typescript-eslint/eslint-plugin": "^8.54.0",
+    "@typescript-eslint/parser": "^8.54.0",
+    "eslint": "^9.39.2",
     "nodemon": "^3.1.9",
     "ts-node": "^10.9.2",
-    "typescript": "^5.7.3"
+    "typescript": "^5.7.3",
+    "vitest": "^4.0.18"
   },
   "scripts": {
     "build": "tsc --build tsconfig.json",
     "start": "node dist/index.js",
-    "dev": "nodemon --exec ts-node src/index.ts"
+    "dev": "nodemon --exec ts-node src/index.ts",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "lint": "eslint src/"
   },
   "dependencies": {
-    "node-fetch": "^3.3.2",
-    "ws": "^8.18.0"
+    "@alpacahq/alpaca-trade-api": "^3.1.3",
+    "dotenv": "^17.2.3"
   }
 }