Stop substituting synthetic market data when providers fail

- Replace synthetic fallback in getQuote()/getPriceHistory() with null returns
- Add QuoteResult/PriceHistoryResult types with { value, stale } structure
- Implement stale-while-revalidate: return cached value with stale=true on live fetch failure
- Cache failures for 30s to avoid hammering provider
- Update CompanyAnalysis type to use PriceData<T> wrapper
- Update task-processors to track failed/stale tickers explicitly
- Update price-history-card UI to show unavailable state and stale indicator
- Add comprehensive tests for failure cases
- Add e2e tests for null data, stale data, and live data scenarios

Resolves #14

lib/server/task-processors.ts

@@ -892,6 +892,8 @@ async function processRefreshPrices(task: Task) {
   const userHoldings = await listHoldingsForPriceRefresh(userId);
   const tickers = [...new Set(userHoldings.map((entry) => entry.ticker))];
   const quotes = new Map<string, number>();
+  const failedTickers: string[] = [];
+  const staleTickers: string[] = [];
   const baseContext = {
     counters: {
       holdings: userHoldings.length
@@ -920,8 +922,15 @@ async function processRefreshPrices(task: Task) {
   );
   for (let index = 0; index < tickers.length; index += 1) {
     const ticker = tickers[index];
-    const quote = await getQuote(ticker);
-    quotes.set(ticker, quote);
+    const quoteResult = await getQuote(ticker);
+    if (quoteResult.value !== null) {
+      quotes.set(ticker, quoteResult.value);
+      if (quoteResult.stale) {
+        staleTickers.push(ticker);
+      }
+    } else {
+      failedTickers.push(ticker);
+    }
     await setProjectionStage(
       task,
       'refresh.fetch_quotes',
@@ -931,7 +940,9 @@ async function processRefreshPrices(task: Task) {
         total: tickers.length,
         unit: 'tickers',
         counters: {
-          holdings: userHoldings.length
+          holdings: userHoldings.length,
+          failed: failedTickers.length,
+          stale: staleTickers.length
         },
         subject: { ticker }
       })
@@ -941,10 +952,12 @@ async function processRefreshPrices(task: Task) {
   await setProjectionStage(
     task,
     'refresh.persist_prices',
-    `Writing refreshed prices for ${tickers.length} tickers across ${userHoldings.length} holdings`,
+    `Writing refreshed prices for ${quotes.size} tickers across ${userHoldings.length} holdings`,
     {
       counters: {
-        holdings: userHoldings.length
+        holdings: userHoldings.length,
+        failed: failedTickers.length,
+        stale: staleTickers.length
       }
     }
   );
@@ -952,12 +965,22 @@ async function processRefreshPrices(task: Task) {
 
   const result = {
     updatedCount,
-    totalTickers: tickers.length
+    totalTickers: tickers.length,
+    failedTickers,
+    staleTickers
   };
 
+  const messageParts = [`Refreshed prices for ${quotes.size}/${tickers.length} tickers`];
+  if (failedTickers.length > 0) {
+    messageParts.push(`(${failedTickers.length} unavailable)`);
+  }
+  if (staleTickers.length > 0) {
+    messageParts.push(`(${staleTickers.length} stale)`);
+  }
+
   return buildTaskOutcome(
     result,
-    `Refreshed prices for ${tickers.length} tickers across ${userHoldings.length} holdings.`,
+    `${messageParts.join(' ')} across ${userHoldings.length} holdings.`,
     {
       progress: {
         current: tickers.length,
@@ -966,7 +989,9 @@ async function processRefreshPrices(task: Task) {
       },
       counters: {
         holdings: userHoldings.length,
-        updatedCount
+        updatedCount,
+        failed: failedTickers.length,
+        stale: staleTickers.length
       }
     }
   );