fix: resolve TODO.md security/perf/test-coverage backlog

Fixes the 13-item codebase health scan backlog: wraps meal-plan
generation in a transaction, adds missing userId/GIN indexes, fixes
an IPv6-parsing gap in the webhook SSRF guard (and an identical
duplicated bug in the AI URL-import path, now consolidated onto one
implementation), paginates the collections list, dedupes the AI
recipe Zod schemas, wires up Stripe tier sync, rate-limits AI key
rotation, gets `pnpm typecheck` actually working, and adds test
coverage for the previously-untested admin/webhooks routes.

Two flagged issues (collection removeRecipeId IDOR, tier-limit race)
turned out to already be fixed/non-issues on inspection — noted in
TODO.md rather than silently dropped.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packages/db/package.json

@@ -12,13 +12,15 @@
     "generate": "drizzle-kit generate",
     "migrate": "drizzle-kit migrate",
     "studio": "drizzle-kit studio",
-    "seed": "tsx src/seed.ts"
+    "seed": "tsx src/seed.ts",
+    "typecheck": "tsc --noEmit"
   },
   "dependencies": {
     "drizzle-orm": "^0.44.7",
     "postgres": "^3.4.7"
   },
   "devDependencies": {
+    "@types/node": "^20.19.43",
     "drizzle-kit": "^0.31.1",
     "tsx": "^4.20.3",
     "typescript": "^5.8.3"