docs(changelog): fragment for #1234

Co-Authored-By: Claude Opus 5.5 <[email protected]>

changelog.d/1234-cctv-catalog-background-refresh.md

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+- Serve the camera catalog while it refreshes. An expired catalog made every
+  camera request wait for the slowest pack to reload; it is now answered at
+  once while one background refresh runs, so only the first load waits. Estonia's
+  slow Tarktee feeds get 30 s instead of 15 s, so the pack no longer drops out
+  on about a third of loads (quanticsoul4772, #1234).