feat: major dependency upgrades, remove Redis, fix mongoose 9 types

Dependencies upgraded:
- svelte 5.38→5.55, @sveltejs/kit 2.37→2.56, adapter-node 5.3→5.5
- mongoose 8→9, sharp 0.33→0.34, typescript 5→6
- lucide-svelte → @lucide/svelte 1.7 (Svelte 5 native package)
- vite 7→8 with rolldown (build time 33s→14s)
- Removed terser (esbuild/oxc default minifier is 20-100x faster)

Infrastructure:
- Removed Redis/ioredis cache layer — MongoDB handles caching natively
- Deleted src/lib/server/cache.ts and all cache.get/set/invalidate usage
- Removed redis-cli from deploy workflow, Redis env vars from .env.example

Mongoose 9 migration:
- Replaced deprecated `new: true` with `returnDocument: 'after'` (16 files)
- Fixed strict query filter types for ObjectId/paymentId fields
- Fixed season param type (string→number) in recipe API
- Removed unused @ts-expect-error in WorkoutSession model

.env.example

@@ -1,10 +1,6 @@
 # Database Configuration
 MONGO_URL="mongodb://user:password@host:port/database?authSource=admin"
 
-# Redis Cache Configuration (optional - falls back to direct DB queries if unavailable)
-REDIS_HOST="localhost"  # Redis server hostname
-REDIS_PORT="6379"       # Redis server port
-
 # Authentication Secrets (runtime only - not embedded in build)
 AUTHENTIK_ID="your-authentik-client-id"
 AUTHENTIK_SECRET="your-authentik-client-secret"