fix(api): persist scratch/local and bound heavy compute concurrency

Keep async job and chart-cache files across API recreates, freeze jyotish_api_server.py growth, and fail fast with 429 when rectification or high-rigor compute is saturated.

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/docker-compose.server.yml

@@ -19,6 +19,11 @@ services:
       retries: 5
       start_period: 30s
       start_interval: 1s
+    volumes:
+      # WORKDIR is /app (deploy/railway-api.Dockerfile). Chart cache, async job
+      # files, and high-rigor job records live under scratch/local. Named volume
+      # is created on first use; previous overlay data was ephemeral.
+      - api_scratch:/app/scratch/local
 
   web:
     image: ${WEB_IMAGE:-jyotisha-web:local}
@@ -68,3 +73,4 @@ services:
 volumes:
   caddy_data:
   caddy_config:
+  api_scratch: