Feat: Generación rápida de combinaciones

[IvanM9]

Generation Flow (POST /api/combinations/generate-quick)

┌─────────────┐
│   Client    │
└──────┬──────┘
       │ POST { occasion: "wedding reception" }
       ▼
┌─────────────────────────────────┐
│  QuickGenerateCombinationDto    │ ← class-validator
│  - occasion: "wedding reception"│
│  - requestAlternative: false    │
└──────┬──────────────────────────┘
       │
       ▼
┌─────────────────────────────────┐
│  CombinationsService            │
│  .generateQuickCombination()    │
└──────┬──────────────────────────┘
       │
       ├─→ Check user wardrobe count (≥5 items?) → Throw error if insufficient
       │
       ├─→ Retrieve GenerationSession from cache (if requestAlternative=true)
       │
       ├─→ Query WardrobeItem (filter by userId, status=true, exclude previous IDs)
       │   └─→ Apply season pre-filtering if wardrobe > 100 items
       │
       ├─→ Call AiService.agent() with prompt + Zod schema
       │   └─→ Retry once on failure (2-second delay)
       │
       ├─→ Validate AI response (3-10 items, valid IDs)
       │
       ├─→ Fetch full item details + images from DB
       │
       ├─→ Update/create GenerationSession in cache
       │
       └─→ Return QuickGenerationResponse
           │
           ▼
       ┌─────────────────────────────────┐
       │  QuickGenerationResponse        │
       │  - outfit: [...]                │
       │  - explanation: "..."           │
       │  - occasion: "wedding reception"│
       └─────────────────────────────────┘

Save Flow (Reuses existing POST /api/combinations/save)

┌─────────────┐
│   Client    │
└──────┬──────┘
       │ POST { name: "...", items: [...], explanation: "..." }
       ▼
┌─────────────────────────────────┐
│  SaveCombinationDto (existing)  │
│  + isAIGenerated: true          │ ← New field added to DTO
│  + occasions: ["..."]           │ ← New field added to DTO
│  + aiDescription: "..."         │ ← Existing field
└──────┬──────────────────────────┘
       │
       ▼
┌─────────────────────────────────┐
│  CombinationsService.save()     │
└──────┬──────────────────────────┘
       │
       ├─→ Create Combination record (isAIGenerated=true, occasions=[...], aiDescription=...)
       │
       ├─→ Create CombinationItem records (one per outfit item)
       │
       ├─→ Delete GenerationSession from cache (FR-011b - session cleared on save)
       │
       └─→ Return saved combination with ID