Fix S&P 500 alerts failing on Alpha Vantage premium endpoint

[valuecodes]

What

• Alpha Vantage moved TIME_SERIES_DAILY&outputsize=full to a paid plan, so the daily sp500-close and sp500-drawdown alerts threw every morning.
• Establish the all-time high from the free TIME_SERIES_WEEKLY history instead, keeping free daily compact bars for the recent closes. Effective ATH = max(pre-window weekly high, recent daily closes).
• The weekly baseline is restricted to weeks ending before the daily window, so today's close can't leak into the "as-of-yesterday" ATH and fabricate a false rebound alert.
• Stays stateless — no KV/persistence added. ~4 API calls/day, well within the free tier.
• Note: deep-history ATH is a weekly-closing-high approximation, not an exact daily-close ATH (accepted trade-off).

How to test

pnpm --filter @repo/alerts test
pnpm --filter @repo/alpha-vantage test
pnpm test

Security review

No security-impacting changes.

[Copilot]

Pull request overview

This PR updates the Alpha Vantage integration and S&P 500 alerts to avoid the now-premium TIME_SERIES_DAILY&outputsize=full endpoint by combining free daily compact bars with the free weekly time series to approximate an all-time-high baseline without adding state/persistence.

Changes:

• Add weekly time-series support to @repo/alpha-vantage (schema + client method) and tests.
• Introduce a shared fetchSp500 helper to fetch daily + weekly series and compute a pre-window ATH baseline.
• Update sp500-close and sp500-drawdown alerts (and tests) to use the new fetch strategy.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/alpha-vantage/src/types.ts	Refactors time-series parsing into a reusable schema and adds weekly response normalization.
packages/alpha-vantage/src/alpha-vantage.ts	Adds getWeeklyTimeSeries() to fetch free long-history weekly data.
packages/alpha-vantage/src/alpha-vantage.test.ts	Extends client tests to cover weekly endpoint behavior and query params.
apps/alerts/src/scheduled.test.ts	Updates Alpha Vantage mock to support the new weekly call used by alerts.
apps/alerts/src/alerts/sp500.ts	Adds shared SPY fetch helper to combine daily compact + weekly history with date cutoff.
apps/alerts/src/alerts/sp500-drawdown.ts	Switches drawdown logic to compute ATH from weekly baseline + recent daily closes.
apps/alerts/src/alerts/sp500-drawdown.test.ts	Updates tests to mock daily+weekly and adds cases for weekly-baseline and date-cutoff behavior.
apps/alerts/src/alerts/sp500-close.ts	Switches close alert to use shared fetch helper and weekly baseline.
apps/alerts/src/alerts/sp500-close.test.ts	Adds dedicated test coverage for close alert with weekly baseline and overlap exclusion.

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