fix: resolve all 58 TypeScript errors across codebase

- Add SvelteKit PageLoad/LayoutLoad/Actions types to recipe route files
- Fix possibly-undefined access on recipe.images, translations.en
- Fix parseFloat on number types in cospend split validation
- Use discriminated union guards for IngredientItem/InstructionItem
- Fix cache invalidation Promise<number> vs Promise<void> mismatch
- Suppress Mongoose model() complex union type error in WorkoutSession

src/routes/api/cospend/payments/+server.ts

@@ -87,7 +87,7 @@ export const POST: RequestHandler = async ({ request, locals }) => {
   // Validate personal + equal split method
   if (splitMethod === 'personal_equal' && splits) {
     const totalPersonal = splits.reduce((sum: number, split: SplitInput) => {
-      return sum + (parseFloat(split.personalAmount) || 0);
+      return sum + (split.personalAmount ?? 0);
     }, 0);
     
     if (totalPersonal > amount) {