feat(history): add /api/history/recent endpoint with Sonarr/Radarr history fetching, tag filtering, and 5-min cache

.env.sample

@@ -52,6 +52,10 @@ COOKIE_SECRET=your-cookie-secret-here
 # Defaults to ./data relative to the project root.
 # DATA_DIR=/app/data
 
+# Number of days of completed download history to show in the Recently Completed section.
+# Override per-request with ?days=N (capped at 90).
+# RECENT_COMPLETED_DAYS=7
+
 # Background polling interval in milliseconds (default: 5000)
 # sofarr polls all services in the background and caches results so
 # dashboard requests are near-instant.