[t0ma5]

Summary

• A monthly expense created on the 31st was clamped to 28 February, and every later month stayed on the 28th. The next date was computed from the previous occurrence, so the original day was lost.
• Store anchorDay on RecurringExpenseLink. February still clamps to the 28th, and March returns to the 31st.
• Editing the expense date on an open series now moves the next occurrence. A series that has already drifted cannot recover its original day.

Test plan

• npm test -- src/lib/recurrence.test.ts
• Apply the Prisma migration 20261012000000_add_recurring_anchor_day
• Create a monthly expense on 31 January and confirm the generated dates are 28 February, then 31 March
• Change that expense date before the next copy is created and confirm the next date follows the new day

[quintushr]

Thanks @t0ma5 for the PR!

I added some tests and added a guard against an infinite loop when the recurrence rule is NONE.