Add Foodbook templates: models, EF migration, service, UI and planner integration

[phoneuooyd]

Motivation

• Provide reusable meal-plan templates so users can save a complete planner and re-apply it for new date ranges.
• Persist templates and template meal positions to the app database so templates survive restarts and can be shared/marked public.
• Expose template management (list / create / edit / delete / apply) in the UI and gate creation via the existing premium checks (IFeatureAccessService).
• Ensure schema is explicit via an EF migration so on-device schema validation can detect the new tables.

Description

• Added domain models FoodbookTemplate and TemplateMeal in FoodbookApp.App/Models/, representing templates and per-day/per-slot recipe positions.
• Added DbSet<FoodbookTemplate> and DbSet<TemplateMeal> plus model configuration (relations, indexes) in Data/AppDbContext.cs and created EF migration Data/Migrations/20260307120000_AddFoodbookTemplates.cs to create FoodbookTemplates and TemplateMeals tables.
• Introduced IFoodbookTemplateService and FoodbookTemplateService implementing template flows: Get, SaveTemplateFromPlanAsync, Update, Remove, and ApplyTemplateAsync which creates a Plan + PlannedMeal[] from a template.
• Added UI and viewmodels: FoodbookTemplatesPage + FoodbookTemplatesViewModel and FoodbookTemplateFormPage + FoodbookTemplateFormViewModel for listing/creating/editing/applying templates.
• Integrated planner actions in PlannerPage (three-dot toolbar): Save current plan as template (premium-gated via IFeatureAccessService) and Apply template (select template and start date to generate a Plan); added a Foodbooks tab in PlannerListsPage and support in PlannerListsViewModel.
• Registered DI and routes in MauiProgram for the new service, viewmodels and pages and updated DatabaseService.RequiredTables to include the new tables.
• Added localization keys for the Foodbooks tab / template form to Localization/PlannerListsPageResources*.resx and updated project docs (DOCS/*) to mention the new feature.

Testing

• Ran a code-style check using git diff --check and fixed trailing whitespace issues (check passed).
• Attempted to run a full build with dotnet build FoodbookApp.App/FoodbookApp.App.csproj but the dotnet CLI is not available in this environment so the build/migrations could not be executed here.
• Attempted an automated UI screenshot with Playwright against a local endpoint, but there was no running app at the target address (result: ERR_EMPTY_RESPONSE), so visual verification was not produced.
• Note: EF migration file 20260307120000_AddFoodbookTemplates was generated and included in the repo, but applying migrations and running integration tests should be executed in CI / a developer machine with the .NET SDK available (run dotnet ef database update or dotnet build + app startup to validate runtime schema).

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Codex Task