Nutrition — per-client plans with macro targets and meals

Nutrition is now a real, end-to-end surface instead of a placeholder:

• Per-client plans. From Coaching → Nutrition, create a plan for any client: a name, optional daily targets (kcal, protein, carbs, fat), a coach note, and as many meals as you like. Each meal carries a time, an item list, and its own calorie count.
• One active plan per client. Assigning a new plan automatically retires the previous one, so a client always sees the current plan and nothing stale.
• Edit without losing work. Opening a plan pre-fills every field — targets, note, and all meals — so edits are real edits, not a blank restart.
• Live in the client app immediately. The client's Nutrition tab shows the plan read-only: a calorie headline, macro rings, the day's meals with a check-off, and your note attributed to you.