Use live limits for fast-mode forecasts

[cbusillo]

Summary

• pass summary.liveLimits into pooled OpenAI fast-mode forecasts
• pass live limits into the app detail forecast path too
• add a regression test for a weekly-exhausted account whose stale 5-hour capacity would otherwise inflate guardrail runway

Context

Review agents caught that PR #91 fixed headline live capacity but fast-mode forecast construction still passed summary.limits, which could re-pool a weekly-blocked account for forecast/runway advice. This PR closes that gap before submitting the 1.0.2 App Store draft.

Verification

• swift test --filter 'openAIFastModeForecastIgnoresFiveHourBucketsBlockedByWeeklyLimit|capacityPortfolioDetailKeepsBurnRateWhenFiveHourGuardrailConstrainWeekly|observedBurnRateIgnoresAccountsExhaustedByLongerWindow|mainLimitSummariesExcludeAccountsExhaustedByLongerOpenAIWindow'
• scripts/commit-gate.sh