fix: prevent horizontal scroll on Public URLs table when filters have long values

[ericokuma]

Fixes the Public URLs settings table overflowing horizontally when filter chips contain long strings (e.g., long publisher IDs).

Changes in PublicURLsResourceTable.svelte:

• table-fixed layout — constrains the table to its container width instead of auto-growing to fit content
• Explicit widths on narrow columns — "Expires on" (108px), "Created by" (108px), "Last accessed" (112px), and the actions column (48px). The three flexible columns (Label, Dashboard, Filters) share the remaining space equally.
• overflow-hidden on cells that may contain long text (Label, Dashboard, Filters, Created by) so content truncates instead of expanding the table
• Constraining wrapper around each filter Chip (max-w-full min-w-0) so individual chips truncate with ellipsis rather than pushing the column wider

Closes APP-805

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

Linear Issue: APP-805