fix(insights,cache): surface revalidation to clients and evict on interactive writes

Stale-served insights responses now carry a revalidating flag; the
advisor and comprehensive queries poll on a bounded 25 s cadence until
the background warm lands, so an open session converges instead of
pinning yesterday's briefing for an hour. Interactive measurement
writes (single create, edit, delete, bulk-delete, restore) hard-evict
the analytics cache so a manually entered value is reflected on the
next read; background batch sync keeps the mark-stale path. The
visit-triggered force warm collapses to one job per user instead of
one per locale, and the umami script proxy failure now annotates a
named action with the failure reason instead of a bare flag.

docs/api/openapi.yaml

@@ -11769,6 +11769,11 @@ components:
           propertyNames:
             type: string
           additionalProperties: {}
+        revalidating:
+          description: True when the body is served from last-good cache (stale-while-revalidate) while a fresh aggregation runs
+            in the background. The client keeps polling on `revalidating` (bounded) so the open page converges on the
+            fresh body.
+          type: boolean
       required:
         - summary
         - recommendations