warn on rollup/base query coverage mismatch

[pjain1]

This is to solve cases when dimensions are served from different tables example one from a rollup another from base because may be that dimension was not present in the rollup or some other criteria. So add a warning in such cases, we return the serving table along with response, UI already know the rollup and base coverage so it can do mismatch check with time coverage of serving table.

Backend changes

Expose which physical table served a metrics query, plus per-rollup time coverage, so the frontend can detect when widgets on one dashboard are served from tables with different retention:

• serving_table added to MetricsViewAggregationResponse, MetricsViewTimeSeriesResponse, and MetricsViewComparisonResponse: the rollup table the query was routed to, empty when served from the base table.
• rollup_time_ranges (map<table, TimeRangeSummary>) added to MetricsViewTimeRange and MetricsViewTimeRanges responses.
• Keys are physical table names throughout matching rollup.Table and ts.Rollups

Frontend warning logic

Each dashboard gets a RollupCoverageStore (on StateManagers) holding per-table time coverage from MetricsViewTimeRange (timeRangeSummary + new rollupTimeRanges) and a registry of which table served each mounted widget (from the new servingTable field on query responses; leaderboards, big numbers, charts, and the dimension table register).

A widget shows the warning if its serving table's coverage starts later than both the requested range start (primary or comparison, whichever is earlier) and the widest coverage among all tables currently in use on the dashboard:

served.min > max(requestedStart, widestInUse.min) + oneGrainBucket(widestTable)

The grain-bucket tolerance suppresses false positives from rollup min timestamps being truncated to bucket starts. Consequences: only widgets actually missing requested data warn; if all widgets route to the same table (e.g. a filter forces everything to base), the dashboard is internally consistent and nothing warns; ranges fully covered by the serving table never warn regardless of table mismatch.

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!