Show active filters as removable chips near Reset filters (#138)

[annpandev]

Summary

Closes #138.

• Adds a row of "chip" pills above the filter bar that summarizes every currently-applied filter (search keywords, investigate/ignore status, outage start date range, platform, outage status, entity level, signal sources).
• Each chip has an "x" to clear just that one filter, without resetting the others or opening its dropdown.
• Chips only render when at least one filter is active; the row is hidden otherwise.

Test plan

• Manually verified each filter type produces the correct chip label
• Manually verified clicking a chip's "x" clears only that filter and leaves the others applied
• Manually verified the chip row disappears when all filters are cleared