Global text-size setting and a weekly meal-plan calendar export

[rjmlaird]

What changed
This patch adds two user-facing features: a global text-size setting and a weekly meal-plan calendar export. It also wires the app startup, theme, settings UI, and Android file-sharing pieces together so both features work end to end.

Why
The text-size setting makes recipe steps easier to read while cooking, and it scales text across the whole app without changing layout spacing. The calendar export gives users a simple way to turn a planned week into an  .ics  file they can share with a calendar app.

How it works
Text size is stored locally in DataStore as a device-only preference, exposed through the settings view models, and applied in  OpenCookTheme  by multiplying the ambient font scale. The meal-plan export builds an RFC 5545  .ics  file for the visible week, writes it to cache, and shares it through a  FileProvider -backed  ACTION_SEND  intent.

Files touched

• MainActivity.kt  now passes the stored text scale into the app theme.
• SettingsRepository.kt  and  ThemeViewModel.kt  add the persisted text-size state.
• SettingsScreen.kt  adds the new settings row and picker dialog.
• Theme.kt  applies the scale at the composition level.
• MealPlanScreen.kt ,  IcsExport.kt ,  IcsShare.kt ,  AndroidManifest.xml , and  file_paths.xml  implement the calendar export flow.
• TextScaleTest.kt  and  IcsExportTest.kt  cover the new behavior.

How to test

1. Open Settings and change the text size; confirm the app text updates immediately.
2. Open Meal Plan, generate a week, then tap the calendar export action.
3. Confirm the exported file can be shared into a calendar app and imports as all-day events.
4. Run the unit tests for  TextScale  and  IcsExport .

Notes

• Text size is local to the device and intentionally not synced with household data.
• The calendar export is a one-shot file export, not a live subscription feed.