fix(miner): repo standing counts match PR table active rows

[carlh7777]

Summary

On the miner details page, per-repository standing cards display Merged and Closed PR counts from the API (totalMergedPrs, totalClosedPrs). These counts are calculated using each repository's configured scoring.pr_lookback_days window (default 30 days via gittensor's PR_LOOKBACK_DAYS, with repository-specific overrides supported).

The Pull Requests table previously used a fixed 35-day staleness window when determining whether merged PRs should appear active or dimmed. As a result, repositories with shorter lookback windows could display merged PRs as active in the table even though they were already excluded from standing counts, leading to inconsistencies between the table and repository standings.

This change aligns PR table staleness styling with repository-specific scoring windows by:

• Resolving pr_lookback_days from repository configuration (/dash/repos)
• Applying repository-specific lookback windows when determining stale merged PRs in MinerPRsTable
• Displaying the effective lookback period on repository standing cards (PR activity · {n}d lookback)
• Updating scoring window utilities to support configurable lookback periods instead of relying on a fixed 35-day threshold

This ensures repository standing counts and Pull Requests table highlighting are derived from the same scoring window logic.

Related Issues

Fixes #1308

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Screenshots

Before

After

Checklist

• New components are modularized/separated where sensible
• Uses predefined theme (e.g. no hardcoded colors)
• Responsive/mobile checked
• Tested against the test API
• npm run format and npm run lint:fix have been run
• npm run build passes
• Screenshots included for any UI/visual changes

[anderdc]

Fix conflicts.

[carlh7777]

@anderdc resolved conflicts, could you review again?

[anderdc]

The core fix is right, but ExplorerUtils.ts changes the defaults of isOutsideScoringWindow and getScoringWindowStartIso from 35 to DEFAULT_PR_LOOKBACK_DAYS (30). Those two are still called with no argument from WatchlistPage (PR + issue staleness), IssuesList, and MinerOpenDiscoveryIssuesByRepo — including the getScoringWindowStartIso() since-filter at line 97 that controls which discovery issues get fetched. So this silently narrows the window by 5 days on surfaces unrelated to #1308. The PR-table fix already routes through the new isOutsidePrLookbackWindow / per-repo map, so these defaults don't need to change — keep both at 35.

[carlh7777]

@anderdc, fixed. could you review again?