## Summary
Adds **catch-all budgets** — a budget flagged `is_catch_all` absorbs
every expense-category transaction not already claimed by another
(non-catch-all) budget, so out-of-budget spending is still tracked.
## Changes
- Migration: `is_catch_all` boolean (default false) on `budgets`.
- `Budget` model: fillable + boolean cast.
- `BudgetTransactionService`: a catch-all budget matches expense
transactions whose `category_id` is not claimed by any non-catch-all
budget; period assignment mirrors the same rule.
- `BudgetController`: supports the flag.
## Notes
- Pre-existing WIP committed as-is; CI is the validation gate.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Víctor Falcón <victoor89@gmail.com>
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