fix: sanitize NaN/inf floats to prevent JSON serialization crashes

SAR (and potentially other EO products) produce NaN/inf from nanmean
on empty pixel slices. These values crash json.dumps() in both the
database write path and the API response path.

Adds sanitize_for_json() utility that recursively replaces NaN/inf
with 0.0, applied at three levels:
- ProductResult model_validator (catches on construction)
- Database save_job_result (catches on storage)
- API get_job endpoint (catches on response)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/api/jobs.py

@@ -1,7 +1,7 @@
 from fastapi import APIRouter, Depends, HTTPException
 from app.api.auth import get_current_user
 from app.database import Database
-from app.models import JobRequest
+from app.models import JobRequest, sanitize_for_json
 
 router = APIRouter(prefix="/api/jobs", tags=["jobs"])
 _db: Database | None = None
@@ -46,7 +46,7 @@ async def get_job(job_id: str, email: str = Depends(get_current_user)):
         "status": job.status.value,
         "progress": job.progress,
         "product_ids": job.request.product_ids,
-        "results": [r.model_dump() for r in job.results],
+        "results": [sanitize_for_json(r.model_dump()) for r in job.results],
         "created_at": job.created_at.isoformat(),
         "updated_at": job.updated_at.isoformat(),
         "error": job.error,

app/database.py

@@ -106,7 +106,8 @@ class Database:
             )
             row = await cursor.fetchone()
             results = json.loads(row[0])
-            results.append(result.model_dump())
+            from app.models import sanitize_for_json
+            results.append(sanitize_for_json(result.model_dump()))
             await db.execute(
                 "UPDATE jobs SET results_json = ?, updated_at = ? WHERE id = ?",
                 (json.dumps(results), now, job_id),

app/models.py

@@ -4,10 +4,30 @@ import enum
 from datetime import date, datetime
 from typing import Any
 
+import math
+
 from pydantic import BaseModel, Field, field_validator, model_validator
 from shapely.geometry import box as shapely_box
 from pyproj import Geod
 
+
+def _sanitize_float(v: Any) -> Any:
+    """Replace NaN/inf float values with 0.0 for JSON compatibility."""
+    if isinstance(v, float) and (math.isnan(v) or math.isinf(v)):
+        return 0.0
+    return v
+
+
+def sanitize_for_json(obj: Any) -> Any:
+    """Recursively sanitize a data structure, replacing NaN/inf with 0.0."""
+    if isinstance(obj, float):
+        return _sanitize_float(obj)
+    if isinstance(obj, dict):
+        return {k: sanitize_for_json(v) for k, v in obj.items()}
+    if isinstance(obj, list):
+        return [sanitize_for_json(v) for v in obj]
+    return obj
+
 # --- East Africa bounding box (approximate) ---
 EA_BOUNDS = (22.0, -5.0, 52.0, 23.0)  # (min_lon, min_lat, max_lon, max_lat)
 MAX_LOOKBACK_DAYS = 3 * 365 + 1  # ~3 years
@@ -130,11 +150,13 @@ class ProductResult(BaseModel):
 
     @model_validator(mode="before")
     @classmethod
-    def _accept_legacy_field_names(cls, data):
-        """Accept old 'indicator_id' field name from stored database records."""
+    def _accept_legacy_and_sanitize(cls, data):
+        """Accept old field names and sanitize NaN/inf floats."""
         if isinstance(data, dict):
             if "indicator_id" in data and "product_id" not in data:
                 data["product_id"] = data.pop("indicator_id")
+            # Sanitize all float values to prevent JSON serialization errors
+            return sanitize_for_json(data)
         return data
     status: StatusLevel
     trend: TrendDirection