feat: implement alert simulation sandbox

[dannyy2000]

What was done

Added a complete alert simulation sandbox that lets operators safely test routing rules against synthetic data before enabling them in production. No real alerts are dispatched during simulation.

Backend — POST /api/v1/admin/alert-routing/simulate

• New dry-run endpoint added to the existing alert routing admin route
• Loads all active routing rules (optionally scoped by ownerAddress)
• Evaluates each rule against the simulated alert using the same matching logic as the live router (severity, assetCode, sourceType)
• Returns per-rule results with human-readable match reasons, effective channels, fallback channels, and suppression window info
• Inactive rules are listed separately (skipped from evaluation) and can be disclosed in the UI
• No DB writes, no channel dispatches — pure evaluation

Frontend — AlertSimulationSandbox page at /alert-sandbox

Left panel — configuration:

• Admin API token input (persisted in localStorage)
• Six scenario presets for common failure modes: Critical Bridge Failure, Token Exploit, TVL Anomaly, Reserve Backing Drift, Gas Price Spike, Scheduled Maintenance
• Full parameter form: severity selector, asset code, source type, triggered value, threshold, metric, owner address, run label

Right panel — Results tab:

• Summary cards: FIRES / SILENT status, rules matched, rules checked
• Simulated input echo bar
• Effective channels panel with suppression window warning
• Per-rule breakdown with green check / grey X indicators and condition-level explanations
• Disclosure toggle for skipped inactive rules

Right panel — History tab:

• Up to 20 simulation runs stored in localStorage via useAlertSimulation hook
• Each entry shows severity, label, asset/source, result, timestamp
• Click any entry to restore its results in the Results tab
• "Clear all" button

Navigation

• "Alert Sandbox" added to the Operations group in navigation.ts
• Route registered in App.tsx

Test plan

• Visit /alert-sandbox — page renders with preset buttons and input form
• Enter admin API token and click "Critical Bridge Failure" preset — fields populate
• Click "Run Simulation" — results panel shows FIRES/SILENT, per-rule cards
• Verify match reasons explain each condition clearly
• Select different severity/asset/source combinations and confirm rule matching changes
• Check suppression window note appears when matched rule has suppressionWindowSeconds > 0
• Switch to History tab — past runs listed, click one to restore results
• Click "Clear all" — history cleared
• Confirm no actual alert is dispatched (check backend logs / audit history)
• Responsive: page adapts correctly on mobile breakpoints

Closes #590

[Mosas2000]

Nice flow, checked it all!