feat: create reconciliation dashboard for reserve drift

[Dannyswiss1]

Description

Adds a reconciliation dashboard so operators can compare on-chain supply, reserve attestations, and reported backing, then triage unresolved drift with drilldowns into source data.

Closes #588

Changes Made

• Added reconciliation drift summary, mismatch detail, and triage status backend endpoints.
• Added reconciliation dashboard UI with asset/bridge/time filters, severity, trend, history, source-data drilldowns, and operator triage controls.
• Added database migration fields for bridge/source metadata, source values, and triage state.
• Wired frontend route/navigation/API types for /reconciliation.
• Documented reconciliation workflow, data model, severity/trend logic, and operator triage process.

Checklist

• PR title follows Conventional Commits format
• Code follows project style
• Build succeeds
• No secrets, credentials, or .env files committed
• Self-review completed

CI Status

• Backend lint, build, and tests pass
• Frontend lint, build, and tests pass