feat: natural language event search

[shan8851]

What

Natural language search bar that translates queries like "USDC transfers over 1M on Ethereum last 24 hours" into structured query params — and runs them.

How

Contract Registry (packages/shared)

• ~28 curated contracts across Ethereum, Polygon, and Base (USDC, USDT, DAI, WETH, Uniswap factories/routers, Permit2, ENS, etc.)
• Fuzzy matching by name, aliases, and address
• Zero-cost local resolution for known contracts

Parse Endpoint (POST /api/parse-query)

• Registry-first: known contracts resolve instantly without any LLM call
• OpenRouter fallback: complex queries (address mentions, conditional filters, unusual contracts) go to a cheap model (Gemini Flash by default)
• Separate rate limiter: 5 parse requests per IP per 15 minutes
• Graceful degradation: if no OpenRouter key, registry matching still works

Arg Filter Engine (packages/shared/src/lib/argFilter.ts)

• Post-query filtering on decoded event args
• Supports: >, <, >=, <=, ==, !=
• Numeric (BigInt), string, and address-aware comparisons
• Handles token decimals scaling (e.g. "over 1M USDC" → value > 1000000000000)

Frontend

• Search bar above the query builder with sparkle icon ✨
• Auto-resolves auto:24h / auto:7d time references into real block numbers
• Populates the existing form and runs the query
• Active filter badges with individual dismiss + clear all
• Manual query builder remains fully functional

Infra

• Rate limiter refactored: configurable per-endpoint with custom messages
• Worker app caching to avoid re-creating Hono app on each request
• OPENROUTER_API_KEY and OPENROUTER_MODEL added to env schema (both optional)

Testing

• 40 tests passing (includes new tests for argFilter, contractRegistry, queryParser, createApp)
• Types clean across all packages

To deploy

# Set OpenRouter key (optional — registry matching works without it)
wrangler secret put OPENROUTER_API_KEY