`num_recommendations` parameter not exposed in frontend UI

[gzark1]

Description

The backend API supports a num_recommendations parameter (3-10 courses per request), but the frontend never passes it and has no UI for users to customize this value.

Steps to Reproduce

1. Open the recommendations chat interface
2. Submit a query or click "Recommend Based on Profile"
3. Observe that you always receive 5 recommendations

Expected Behavior

Users should be able to specify how many recommendations they want (3-10), or the system should clearly document that 5 is the fixed count.

Actual Behavior

• Backend accepts num_recommendations with range 3-10, default 5
• Frontend type defines num_recommendations?: number but never sends it
• No UI control exists for users to change the count
• Users always get 5 recommendations with no option to adjust

Root Cause

• frontend/src/features/recommendations/components/recommendation-chat.tsx:79 - only passes { query }
• frontend/src/features/recommendations/components/recommendation-chat.tsx:94 - passes {}
• frontend/src/features/recommendations/components/recommendation-input.tsx - no input control for count

Possible Solutions

1. Option A - Implement in frontend: Add a slider/dropdown (3-10) in the recommendation input component and pass num_recommendations in the API request

2. Option B - Remove from backend: Remove the parameter from RecommendationRequest schema and hardcode 5 throughout, simplifying the API