feat(jurisdiction.toml): consolidated [shared.timing] section for renewal/expungement/dashboard windows

Source: adr-011-hardcoded-policy-values-sweep plan Potential Improvements.

The hardcoded-policy-values audit identified that renewal, expungement, and dashboard-lookahead window values are duplicated across 4+ jurisdiction.toml sections (snap, tanf, medicaid, etc.). Phase 5 of the sweep externalised individual values; consolidating them under a single [shared.timing] section with citations would reduce duplication and the risk of section-to-section drift.

Acceptance: [shared.timing] section in jurisdiction.toml with renewal-window / expungement-clock / dashboard-lookahead values; per-program sections reference shared.* via the policy resolver; cargo xtask policy audit validates the new shape.