Fix dashboard date ranges with dynamic D1 queries

[tevnull]

Summary

• make the dashboard route loader depend on the selected timeframe URL parameters
• query D1 with an indexed start/end range instead of loading a fixed history window
• keep the default dashboard view at 30 days while allowing custom ranges longer than 90 days
• keep OPENAI_USAGE_DAYS_BACK scoped to optional OpenAI synchronization
• validate calendar dates before they reach server-side date arithmetic
• preserve custom dates in URL state and remove snapshot-derived input bounds that blocked older ranges

Behavior

• 24h, 7d, 30d, and 90d request their matching source windows
• preset=custom&startDay=YYYY-MM-DD&endDay=YYYY-MM-DD requests that exact inclusive date range
• timeframe navigation reruns the TanStack route loader and server function
• publisher and ingestion behavior are unchanged

Verification

• npm test — 31/31 passed
• npm run typecheck — passed
• npm run lint — passed
• npm run build — passed
• npx wrangler deploy --dry-run — passed
• git diff --check origin/main — passed
• SQLite EXPLAIN QUERY PLAN confirms the bounded read uses daily_usage_rollups_workspace_day_idx

Notes

Repository-wide Prettier checks have existing baseline drift in the touched TypeScript files; this change does not perform a drive-by full-file reformat.

[github-actions]

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