feat: add combined environment endpoint for concurrent weather + air quality fetch

- POST /volatile/fetch/environment/{city} fetches both in parallel
- Single geocode lookup shared between API calls
- Uses asyncio.gather() for concurrent external requests
- Fix scheduler executor name (rest_api → rest_api_executor)

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

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

src/services/volatile_fetch_service.py

@@ -5,9 +5,10 @@ Orchestrates fetching data from external APIs and storing in volatile cache.
 Called by scheduler for prefetch or by HybridRAG for reactive caching.
 """
 
+import asyncio
 import logging
 from typing import Optional
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 
 from src.apis import (
     OpenMeteoProvider,
@@ -36,6 +37,16 @@ class FetchResult:
     error: Optional[str] = None
 
 
+@dataclass
+class EnvironmentFetchResult:
+    """Result of combined environment fetch (weather + air quality)."""
+    success: bool
+    key: str
+    weather: Optional[FetchResult] = None
+    air_quality: Optional[FetchResult] = None
+    errors: list[str] = field(default_factory=list)
+
+
 class VolatileFetchService:
     """
     Service to fetch external data and store in volatile cache.
@@ -596,3 +607,130 @@ class VolatileFetchService:
                 key=city.lower(),
                 error=str(e)
             )
+
+    async def fetch_environment(
+        self,
+        user: str,
+        city: str,
+        weather_ttl: int = 3600,
+        air_quality_ttl: int = 3600,
+    ) -> EnvironmentFetchResult:
+        """
+        Fetch weather and air quality concurrently for a city.
+
+        Performs a single geocode lookup and fetches both weather and air quality
+        data in parallel, storing both in volatile cache.
+
+        Args:
+            user: User identifier
+            city: City name (will be geocoded once)
+            weather_ttl: TTL for weather data (default 1 hour)
+            air_quality_ttl: TTL for air quality data (default 1 hour)
+
+        Returns:
+            EnvironmentFetchResult with both weather and air quality results
+        """
+        errors: list[str] = []
+        key = city.lower()
+
+        # Single geocode lookup (shared by both fetches)
+        try:
+            location = await self.weather.geocode(city)
+            if not location:
+                return EnvironmentFetchResult(
+                    success=False,
+                    key=key,
+                    errors=[f"Could not geocode city: {city}"]
+                )
+        except Exception as e:
+            return EnvironmentFetchResult(
+                success=False,
+                key=key,
+                errors=[f"Geocoding failed: {e}"]
+            )
+
+        # Fetch weather and air quality concurrently
+        async def fetch_weather_data() -> FetchResult:
+            try:
+                current = await self.weather.get_current(location)
+                text = current.to_text()
+                data = {
+                    "temperature": current.temperature,
+                    "feels_like": current.feels_like,
+                    "humidity": current.humidity,
+                    "wind_speed": current.wind_speed,
+                    "wind_direction": current.wind_direction,
+                    "conditions": current.condition_text,
+                    "condition_code": current.condition.value,
+                    "uv_index": current.uv_index,
+                    "location": current.location,
+                    "text": text,
+                }
+                record = await self.volatile.store(
+                    user=user,
+                    namespace=VolatileNamespace.WEATHER,
+                    key=key,
+                    data=data,
+                    source="openmeteo",
+                    ttl=weather_ttl,
+                )
+                return FetchResult(success=True, namespace="weather", key=key, record=record)
+            except Exception as e:
+                return FetchResult(success=False, namespace="weather", key=key, error=str(e))
+
+        async def fetch_air_quality_data() -> FetchResult:
+            try:
+                air_quality = await self.weather.get_air_quality(location)
+                data = {
+                    "location": air_quality.location,
+                    "aqi_european": air_quality.aqi_european,
+                    "aqi_us": air_quality.aqi_us,
+                    "pm2_5": air_quality.pm2_5,
+                    "pm10": air_quality.pm10,
+                    "ozone": air_quality.ozone,
+                    "nitrogen_dioxide": air_quality.nitrogen_dioxide,
+                    "sulphur_dioxide": air_quality.sulphur_dioxide,
+                    "carbon_monoxide": air_quality.carbon_monoxide,
+                    "pollen_grass": air_quality.pollen_grass,
+                    "pollen_birch": air_quality.pollen_birch,
+                    "pollen_alder": air_quality.pollen_alder,
+                    "text": air_quality.to_text(),
+                }
+                record = await self.volatile.store(
+                    user=user,
+                    namespace=VolatileNamespace.AIR_QUALITY,
+                    key=key,
+                    data=data,
+                    source="openmeteo",
+                    ttl=air_quality_ttl,
+                )
+                return FetchResult(success=True, namespace="air_quality", key=key, record=record)
+            except Exception as e:
+                return FetchResult(success=False, namespace="air_quality", key=key, error=str(e))
+
+        # Run both fetches concurrently
+        weather_result, air_quality_result = await asyncio.gather(
+            fetch_weather_data(),
+            fetch_air_quality_data(),
+        )
+
+        # Collect any errors
+        if not weather_result.success:
+            errors.append(f"Weather: {weather_result.error}")
+        if not air_quality_result.success:
+            errors.append(f"Air quality: {air_quality_result.error}")
+
+        success = weather_result.success or air_quality_result.success
+        logger.info(
+            f"Environment fetch for {city} (user={user}): "
+            f"weather={'ok' if weather_result.success else 'failed'}, "
+            f"air_quality={'ok' if air_quality_result.success else 'failed'}"
+        )
+
+        return EnvironmentFetchResult(
+            success=success,
+            key=key,
+            weather=weather_result,
+            air_quality=air_quality_result,
+            errors=errors,
+        )