Replaces 33 for...in loops across 18 files with for...of + Object.keys/entries
or indexed for loops. for...in iterates enumerable string keys including
inherited ones, which is especially risky on reactive arrays (tasks, labels,
assignees, etc.) where polyfilled properties may appear.
Loops that mutate via splice during iteration now iterate backwards to avoid
index-shift bugs. Adds a no-restricted-syntax ESLint rule forbidding
ForInStatement to prevent regressions.
Closes#513
2c6029eac4