Allow subcategories to inherit parent budget without individual limits (#579)

* Initial plan

* Implement subcategory budget inheritance feature

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Fix available_to_spend calculation for parent categories with mixed subcategories

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Optimize budget category calculations to avoid redundant filtering

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Add documentation for subcategory budget inheritance feature

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Add edge case tests for budget inheritance feature

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Fix linting issues - remove trailing whitespace

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Replace hardcoded '(shared)' label with i18n translation

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Fix test failures due to duplicate category names

Use unique names with timestamps to avoid validation errors when creating test categories. The Category model has a uniqueness validation on name scoped to family_id, and the test fixtures already contain categories like "Restaurants" which were causing conflicts.

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Remove LLM `.md` spec file

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Juan José Mata <jjmata@jjmata.com>

config/locales/views/reports/en.yml

@@ -34,6 +34,7 @@ en:
       budgeted: Budgeted
       remaining: Remaining
       over_by: Over by
+      shared: shared
       suggested_daily: "%{amount} suggested per day for %{days} remaining days"
       no_budgets: No budget categories set up for this month
       status: