v0.24.0

Added

• Budget: expense categories are now stored in the database (budget_categories table) as stable English slugs, replacing hardcoded German strings
• Budget: subcategory support for all expense entries — 35 predefined subcategories across 8 top-level categories (housing, food, transport, personal_health, leisure, shopping_clothing, education, financial_other)
• Budget: users can add custom categories and subcategories directly from the entry modal via inline "+ category" / "+ subcategory" buttons
• Budget: new API endpoints POST /api/v1/budget/categories and POST /api/v1/budget/categories/:key/subcategories for custom category/subcategory creation
• Budget: subcategory displayed alongside category in each entry's metadata line
• Budget: CSV export now includes a subcategory column and English column headers
• i18n: all 14 non-German locales extended with new budget category keys (catHousing, catTransport, catPersonalHealth, catShoppingClothing, catFinancialOther) and all 35 subcategory label keys
• All server-side log messages and API error strings translated from German to English — contributed by @rafaelfoster

Changed

• Budget category labels for existing entries migrated to new slug keys via DB migration 15; display names remain fully localised through the i18n system