Fix Mixpanel analytics review findings FRE-5281

P0: Fix validation bypass - validated properties now override raw properties
P1: Add unit tests for shared-analytics package (3 test files)
P1: Refactor spamshield to use shared-analytics, deprecate duplicate
P2: Normalize phone numbers to E.164 before hashing
P2: Add graceful error handling for missing env vars in config
P3: Add singleton pattern to MixpanelService
P3: Include timestamp in validated properties schema

packages/shared-analytics/package.json

@@ -6,7 +6,10 @@
   "main": "src/index.ts",
   "types": "src/index.ts",
   "scripts": {
-    "lint": "eslint src/"
+    "lint": "eslint src/",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "typecheck": "tsc --noEmit"
   },
   "dependencies": {
     "@segment/analytics-node": "^1.0.0",
@@ -14,6 +17,8 @@
     "zod": "^4.3.6"
   },
   "devDependencies": {
-    "typescript": "^5.3.3"
+    "typescript": "^5.3.3",
+    "vitest": "^4.1.5",
+    "@vitest/coverage-v8": "^4.1.5"
   }
 }