fix(growth): require a 1000-view baseline on the rate board

Keep small-base videos on the delta board only, and raise the smoothing prior to 1000 so videos that just clear the floor do not dominate the ranking.

config.docker.example.jsonc

@@ -108,6 +108,6 @@
     "video_shrink_minutes": 60,
     "shrink_minutes": null,
     "home_growth_days": "auto",
-    "growth_rate_prior": 500,
+    "growth_rate_prior": 1000,
   },
 }