diet/recipe: Encapsulate infra exports — export only factories

[marcuscastelo]

Summary

Refactor the diet/recipe module infrastructure to encapsulate implementation details: export only factory functions and keep helper functions file-local.

Part of #1403

Scope / Representative files

• src/modules/diet/recipe/infrastructure/recipeRepository.ts
• src/modules/diet/recipe/infrastructure/supabase/supabaseRecipeGateway.ts
• src/modules/diet/recipe/infrastructure/supabase/supabaseRecipeMapper.ts
• src/modules/diet/recipe/infrastructure/signals/recipeCacheStore.ts
• src/modules/diet/recipe/infrastructure/supabase/realtime.ts

Deliverables

• Export only factories (e.g., createRecipeRepository, createSupabaseRecipeGateway).
• Update call-sites to use returned instances.
• Ensure TypeScript/lint/tests pass.

Acceptance Criteria

• No internal helper functions are exported from infra files.