feat(meal): meal plan dashboard page with calendar-aware timing

[the-mrinal]

Summary

• Adds a fifth dashboard tab (Meals) that fetches a JSON meal plan from a user-configured URL and displays today's plan on a cream-paper layout.
• Picks the day's "Up next" meal by cross-referencing the calendar event timeline, with countdown updates ("in 1h 23m") and a "happening now" state.
• Page lives in its own visual world: hides the global Unsplash wallpaper + credit while active, and ships its own Fraunces/Newsreader typography.

What's in the box

• New screen + binder (MealScreenBinder, screen_meal.xml, item_meal_row.xml, item_meal_prep.xml).
• Plan pipeline: MealPlanFetcher → MealPlanParser → MealPlanRepository → MealPlanCenter → MealPlanPoller, with stale-cache banner + parse-error empty state.
• MealEventTimeline picks the active/next meal based on calendar events (unit-tested in MealEventTimelineTest).
• Settings entry: Meal plan → Meal plan JSON URL (leave blank to hide the tab); editing the URL re-publishes immediately.
• D-pad up/down scrolls the meal list, matching the calendar page UX.
• usesCleartextTraffic=true added to manifest so HTTP-hosted plans work alongside HTTPS.

Test plan

• Open Settings → Meal plan, paste a meal-plan.json URL, return to dashboard — Meals tab populates.
• Clear the URL — Meals tab shows the empty-state pointing back to settings.
• Point the URL at unreachable host — fetch-error state appears; recovers after URL fix.
• Point at malformed JSON — parse-error state appears.
• Have a calendar event scheduled, verify "Up next" countdown updates and flips to "happening now".
• Navigate to Meals page — Unsplash wallpaper + credit hidden; navigate away — they restore.
• D-pad up/down scrolls the meal list on the Meals page.
• ./gradlew test — MealEventTimelineTest passes.

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