ENH - add slow VaultX market cycles

Drive server-authoritative prices through alternating global and per-market trend phases with eased transitions, reduced noise, momentum, mean reversion, and rare bounded shocks. Mirror the cycle model in browser mocks and slow development preview ticks so charts show readable highs and downs.

frontend/testserver/index.cjs

@@ -496,8 +496,43 @@ const cryptoMarkets = [
     supply: 1200000000,
   }),
 ]
+const cryptoMarketDynamics = new Map()
+const cryptoGlobalCycle = {
+  bias: 0,
+  direction: 0,
+  remainingTicks: 0,
+  target: 0,
+}
+function advanceCryptoCycle(
+  cycle,
+  minimumTicks,
+  maximumTicks,
+  minimumStrength,
+  maximumStrength,
+) {
+  if (cycle.remainingTicks <= 0) {
+    cycle.direction =
+      cycle.direction === 0 ? (Math.random() < 0.5 ? -1 : 1) : -cycle.direction
+    cycle.remainingTicks = Math.floor(
+      minimumTicks + Math.random() * (maximumTicks - minimumTicks + 1),
+    )
+    cycle.target =
+      cycle.direction *
+      (minimumStrength + Math.random() * (maximumStrength - minimumStrength))
+  }
+  cycle.bias += (cycle.target - cycle.bias) * 0.18
+  cycle.remainingTicks -= 1
+  return cycle.bias
+}
 function advanceCryptoMarkets() {
   const updatedAt = Date.now()
+  const globalBias = advanceCryptoCycle(
+    cryptoGlobalCycle,
+    24,
+    54,
+    0.00008,
+    0.00024,
+  )
   for (const market of cryptoMarkets) {
     const currentPrice = Number(market.price)
     const fractionDigits = currentPrice < 1 ? 4 : 2
@@ -510,8 +545,31 @@ function advanceCryptoMarkets() {
           : currentPrice >= 1
             ? 0.0012
             : 0.004
-    const direction = Math.random() < 0.49 ? -1 : 1
-    const movement = direction * volatility * (0.25 + Math.random() * 0.75)
+    const dynamics = cryptoMarketDynamics.get(market.id) ?? {
+      bias: 0,
+      direction: 0,
+      momentum: 0,
+      remainingTicks: 0,
+      target: 0,
+    }
+    const cycleBias = advanceCryptoCycle(
+      dynamics,
+      14,
+      30,
+      volatility * 0.28,
+      volatility * 0.52,
+    )
+    const impulse = (Math.random() * 2 - 1) * volatility * 0.2
+    dynamics.momentum = dynamics.momentum * 0.8 + impulse * 0.2
+    cryptoMarketDynamics.set(market.id, dynamics)
+    const movement = Math.max(
+      -volatility * 0.9,
+      Math.min(
+        volatility * 0.9,
+        cycleBias + globalBias + dynamics.momentum + impulse,
+      ),
+    )
+    const direction = movement < 0 ? -1 : 1
     let nextPrice = Number(
       Math.max(minimumStep, currentPrice * (1 + movement)).toFixed(
         fractionDigits,