## Problem
Four filter dropdown components were calling `JSON.parse(filter.value)
as string[]` to parse stored filter state. This throws a `SyntaxError`
if the value is malformed (truncated URL, stale localStorage, migration
artifact), crashing the entire dropdown with no recovery.
## Solution
Replace with the existing `parseJson<string[]>` utility from
`twenty-shared`, which wraps `JSON.parse` in a try/catch and returns
`null` on failure. The `?? []` fallback gracefully degrades to an empty
selection instead of crashing.
All four files had an explicit `// TODO: replace by a safe parse`
marking this as a known issue.
## Testing
No new tests — `parseJson` is already tested in `twenty-shared`. No new
logic introduced.
## issue link
#18514
