feat: separate current weather from forecast into distinct namespaces

- Add FORECAST namespace for multi-day outlook (12hr TTL)
- WEATHER namespace now stores only current conditions (1hr TTL)
- Split fetch_weather into fetch_current_weather + fetch_forecast
- Add POST /volatile/fetch/forecast/{city} endpoint
- Different update frequencies for efficient caching

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_volatile.py

@@ -98,7 +98,7 @@ class TestVolatileNamespaces:
 
     def test_weather_default_ttl(self):
         """Test weather namespace default TTL."""
-        assert NAMESPACE_DEFAULT_TTL[VolatileNamespace.WEATHER] == 1800  # 30 min
+        assert NAMESPACE_DEFAULT_TTL[VolatileNamespace.WEATHER] == 3600  # 1 hour (current conditions)
 
     def test_financial_default_ttl(self):
         """Test financial namespace default TTL."""
@@ -110,7 +110,7 @@ class TestVolatileNamespaces:
 
     def test_namespace_count(self):
         """Test we have the expected number of namespaces."""
-        assert len(VolatileNamespace) == 12  # Including SUN for sunrise/sunset
+        assert len(VolatileNamespace) == 13  # Including SUN, FORECAST
 
 
 class TestVolatileListResponse:
@@ -274,7 +274,7 @@ class TestVolatileService:
     def test_get_default_ttl_known_namespace(self, volatile_service):
         """Test default TTL for known namespace."""
         ttl = volatile_service._get_default_ttl("weather")
-        assert ttl == 1800  # Weather namespace default
+        assert ttl == 3600  # Weather namespace default (1 hour)
 
     def test_get_default_ttl_unknown_namespace(self, volatile_service):
         """Test default TTL for unknown namespace."""
@@ -366,7 +366,7 @@ class TestVolatileService:
             ttl=None  # Not specified
         )
 
-        assert result.ttl == 1800  # Weather default
+        assert result.ttl == 3600  # Weather default (1 hour)
 
     @pytest.mark.asyncio
     async def test_search_empty_collection(self, volatile_service, mock_qdrant, mock_ollama):