feat: implement hybrid oracle AMM with CoinGecko prices

- Add priceOracle service for fetching CoinGecko prices
- Update SwapInterface to use oracle prices instead of pool reserves
- All swaps route through USDT as base currency
- Multi-hop routing for non-USDT pairs (X → USDT → Y)
- Display real-time USD prices from CoinGecko
- Auto-refresh prices every 30 seconds

shared/lib/priceOracle.ts

@@ -0,0 +1,170 @@
+/**
+ * Price Oracle Service - Fetches prices from CoinGecko
+ * USDT-based Hybrid Oracle AMM
+ */
+
+const COINGECKO_API = 'https://api.coingecko.com/api/v3';
+
+// CoinGecko ID mappings
+export const COINGECKO_IDS: Record<string, string> = {
+  'wDOT': 'polkadot',
+  'wETH': 'ethereum',
+  'wBTC': 'bitcoin',
+  'wUSDT': 'tether',
+  'USDT': 'tether',
+};
+
+// Manual prices for tokens not on CoinGecko (in USD)
+export const MANUAL_PRICES: Record<string, number> = {
+  'HEZ': 1.0,     // Set your HEZ price
+  'PEZ': 0.10,    // Set your PEZ price
+  'wHEZ': 1.0,
+};
+
+// Price cache
+interface PriceCache {
+  prices: Record<string, number>;
+  timestamp: number;
+}
+
+let priceCache: PriceCache | null = null;
+const CACHE_TTL = 60 * 1000; // 1 minute cache
+
+/**
+ * Fetch prices from CoinGecko
+ */
+export async function fetchCoinGeckoPrices(): Promise<Record<string, number>> {
+  try {
+    const ids = [...new Set(Object.values(COINGECKO_IDS))].join(',');
+    const response = await fetch(
+      `${COINGECKO_API}/simple/price?ids=${ids}&vs_currencies=usd`
+    );
+
+    if (!response.ok) {
+      throw new Error(`CoinGecko API error: ${response.status}`);
+    }
+
+    const data = await response.json();
+    const prices: Record<string, number> = {};
+
+    for (const [symbol, cgId] of Object.entries(COINGECKO_IDS)) {
+      if (data[cgId]?.usd) {
+        prices[symbol] = data[cgId].usd;
+      }
+    }
+
+    return prices;
+  } catch (error) {
+    console.error('CoinGecko fetch failed:', error);
+    return {};
+  }
+}
+
+/**
+ * Get all token prices (CoinGecko + manual)
+ */
+export async function getAllPrices(): Promise<Record<string, number>> {
+  // Check cache
+  if (priceCache && Date.now() - priceCache.timestamp < CACHE_TTL) {
+    return priceCache.prices;
+  }
+
+  const coinGeckoPrices = await fetchCoinGeckoPrices();
+  const prices: Record<string, number> = {
+    ...MANUAL_PRICES,
+    ...coinGeckoPrices,
+  };
+
+  // USDT is always $1
+  prices['USDT'] = 1;
+  prices['wUSDT'] = 1;
+
+  priceCache = { prices, timestamp: Date.now() };
+  return prices;
+}
+
+/**
+ * Calculate swap using oracle prices
+ * All swaps go through USDT as base currency
+ */
+export async function calculateOracleSwap(
+  fromSymbol: string,
+  toSymbol: string,
+  fromAmount: number,
+  feePercent: number = 0.3
+): Promise<{
+  toAmount: number;
+  rate: number;
+  fromPriceUsd: number;
+  toPriceUsd: number;
+  route: string[];
+} | null> {
+  const prices = await getAllPrices();
+
+  const fromPrice = prices[fromSymbol];
+  const toPrice = prices[toSymbol];
+
+  if (!fromPrice || !toPrice) {
+    console.warn(`Price not found: ${fromSymbol}=$${fromPrice}, ${toSymbol}=$${toPrice}`);
+    return null;
+  }
+
+  // Calculate rate and output
+  const rate = fromPrice / toPrice;
+  const feeMultiplier = 1 - (feePercent / 100);
+
+  // Determine route
+  let route: string[];
+  let totalFee = feePercent;
+
+  if (fromSymbol === 'USDT' || fromSymbol === 'wUSDT') {
+    // Direct: USDT → X
+    route = [fromSymbol, toSymbol];
+  } else if (toSymbol === 'USDT' || toSymbol === 'wUSDT') {
+    // Direct: X → USDT
+    route = [fromSymbol, toSymbol];
+  } else {
+    // Multi-hop: X → USDT → Y (double fee)
+    route = [fromSymbol, 'USDT', toSymbol];
+    totalFee = feePercent * 2;
+  }
+
+  const actualFeeMultiplier = 1 - (totalFee / 100);
+  const toAmount = fromAmount * rate * actualFeeMultiplier;
+
+  return {
+    toAmount,
+    rate,
+    fromPriceUsd: fromPrice,
+    toPriceUsd: toPrice,
+    route,
+  };
+}
+
+/**
+ * Get exchange rate between two tokens
+ */
+export async function getExchangeRate(
+  fromSymbol: string,
+  toSymbol: string
+): Promise<number | null> {
+  const prices = await getAllPrices();
+  const fromPrice = prices[fromSymbol];
+  const toPrice = prices[toSymbol];
+
+  if (!fromPrice || !toPrice) return null;
+  return fromPrice / toPrice;
+}
+
+/**
+ * Format USD price for display
+ */
+export function formatUsdPrice(price: number): string {
+  if (price >= 1000) {
+    return `$${price.toLocaleString('en-US', { maximumFractionDigits: 2 })}`;
+  } else if (price >= 1) {
+    return `$${price.toFixed(2)}`;
+  } else {
+    return `$${price.toFixed(4)}`;
+  }
+}