feat: 90-day price range Y-axis scaling with breakthrough annotations

Backend:
- GET /api/market/prices/{ticker} now returns { bars, range_90d }
  with 90-day low/high computed from market_snapshots
- POST /api/market/backfill/{ticker} fetches 90 days of daily bars
  from Polygon and inserts missing bars into market_snapshots
- POST /api/market/backfill-all does the same for all active tickers

Frontend:
- Right Y-axis domain scaled to 90-day min/max (with 3% padding)
- Green dashed reference line at 90-day high
- Red dashed reference line at 90-day low
- Labels show exact price on each reference line
- Default limit bumped to 200 bars

frontend/src/api/hooks.ts

@@ -256,8 +256,13 @@ export interface MarketPrice {
   captured_at: string;
 }
 
-export function useMarketPrices(ticker: string | undefined, limit = 30) {
-  return useGet<MarketPrice[]>(
+export interface MarketPriceResponse {
+  bars: MarketPrice[];
+  range_90d: { low: number | null; high: number | null };
+}
+
+export function useMarketPrices(ticker: string | undefined, limit = 200) {
+  return useGet<MarketPriceResponse>(
     ['market-prices', ticker, limit],
     'query',
     `/api/market/prices/${ticker}?limit=${limit}`,
@@ -265,6 +270,18 @@ export function useMarketPrices(ticker: string | undefined, limit = 30) {
   );
 }
 
+/** Backfill 90 days of daily bars from Polygon for a single ticker. */
+export function useBackfillMarketPrices() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (ticker: string) =>
+      apiPost<{ ticker: string; inserted: number; total_bars: number }>('query', `/api/market/backfill/${ticker}`, {}),
+    onSuccess: (_data, ticker) => {
+      qc.invalidateQueries({ queryKey: ['market-prices', ticker] });
+    },
+  });
+}
+
 export function useTrend(id: string | undefined) {
   return useGet<TrendSummary>(['trend', id], 'query', `/api/trends/${id}`, !!id);
 }