[AmrMsCLL]

Second of three Spending clean-ups. Spending stays on for everyone; budgets inside it are now opt-in by use.

• Budgets only when set: the overview shows Left to spend and Safe to spend a day only when the month has a budget. Without one it shows Spent and Received.
• Budgets tab: lists only categories that have a budget. With no budgets at all it says budgets are optional and what they add. Set a budget is the primary button and picks the category in its dialog; the per-row "Set a budget" on unbudgeted categories is gone.
• By category is a chart: one stacked bar of this month's spending by category, in the categories' own colours, with a legend of amount and share. The top seven categories show; the rest fold into "N more". Hovering a segment shows its amount.
• By category is optional: Hide on the section, or Hide/Show spending by category in the page menu. The choice is kept per browser.
• Custom categories: Edit categories moved from the Budgets tab to the page menu.

Specs: spending. Three tests follow the new layout (the overview no longer has the per-category meter; Set a budget and Edit categories moved), and one new test covers a month with no budget and the chart toggle.