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

vite.config.ts

@@ -10,14 +10,7 @@ export default defineConfig({
 		exclude: ['barcode-detector']
 	},
 	build: {
-		minify: 'terser',
-		terserOptions: {
-			compress: {
-				drop_console: ['log', 'debug'],
-				drop_debugger: true
-			}
-		},
-		rollupOptions: {
+		rolldownOptions: {
 			output: {
 				manualChunks: (id) => {
 					// Separate large dependencies into their own chunks