Cache economic calendar for 1 hour, fix SCAN_BUTTONS test for EUR-only

The weekly calendar JSON was re-fetched on every scan cycle (~288
calls/day). Now cached per-instance with 1-hour TTL, cutting to ~24.
Currency filtering still applied on each read so cached events stay
correct across pairs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

news_engine.py

@@ -127,6 +127,7 @@ class NewsEngine:
     }
 
     _calendar_backoff_until: float = 0.0
+    _CALENDAR_CACHE_TTL: float = 3600.0
 
     def __init__(self, config: NewsConfig):
         self.config = config
@@ -134,6 +135,8 @@ class NewsEngine:
         self._session.headers.update({
             "User-Agent": "Mozilla/5.0 (compatible; ForexIntel/1.0)"
         })
+        self._calendar_cache: List[EconomicEvent] = []
+        self._calendar_cache_time: float = 0.0
 
     def get_fundamental_context(
         self, currencies: Optional[List[str]] = None
@@ -278,11 +281,20 @@ class NewsEngine:
         Tries Forex Factory first, falls back to MyFXBook RSS.
         Returns an empty list (with a log warning) if unavailable —
         we never generate fake events since that causes constant false alarms.
+
+        Results are cached for 1 hour since the weekly calendar rarely changes.
         """
+        now = time.time()
+        if self._calendar_cache and (now - self._calendar_cache_time) < self._CALENDAR_CACHE_TTL:
+            return [e for e in self._calendar_cache if e.currency in currencies]
+
         for fetcher in (self._try_fetch_calendar_api, self._try_fetch_myfxbook_rss):
             try:
                 events = fetcher()
                 if events:
+                    self._calendar_cache = events
+                    self._calendar_cache_time = now
+                    logger.debug(f"Calendar cached: {len(events)} events (TTL {self._CALENDAR_CACHE_TTL:.0f}s)")
                     return [e for e in events if e.currency in currencies]
             except Exception as e:
                 logger.debug(f"Calendar fetch exception ({fetcher.__name__}): {e}")

test_all.py

@@ -1475,7 +1475,7 @@ def _():
 
 @test("SCAN_BUTTONS and SCAN_LOOKUP consistency")
 def _():
-    assert len(SCAN_BUTTONS) == 10  # 5 per pair (4 TFs + All) × 2 pairs
+    assert len(SCAN_BUTTONS) == 5  # 4 TFs + All for EUR/USD
     for btn in SCAN_BUTTONS:
         assert btn["cb"] in SCAN_LOOKUP
         assert "symbol" in btn