[ISSUE-031] Meal Plan Generation Flow

## Phase 5: AI Infrastructure & Meal Planning (Weeks 7-9)

### Description
Create meal plan generation screen
Add loading states and progress indicators
Implement meal plan preview before saving
Add regeneration/alternative suggestion options
Allow manual meal swapping

### Dependencies
- #030

### Can Work in Parallel With
- #032

Start by reviewing dependency #030 and the project structure to locate the meal plan generation screen. Implement the listed flow: loading and progress states, a preview before saving, regeneration or alternatives, and manual meal swapping; done means each interaction works together in the generation flow.

Written by the indexing model from the issue text.