release: 1.6.0: 30-day send stats and optional auto level-2 rate limits

30-day sending statistics per domain and application, plus optional auto level-2 rate limits derived from average send rate.
Added:
  - Domain page **Sending statistics** card: total messages, peak and average
  - Level-2 rate limit **Manual** / **Auto** mode on domain and application
  - Domain export JSON now includes rate limits (`mode`, `auto_multiplier`,
Changed:
  - Auto mode uses the level-1 window (`RATE_LIMIT_WINDOW_SECONDS`); manual

Full detail: CHANGELOG.md (1.6.0).

internal/web/view/static/panel.js

@@ -61,6 +61,16 @@
       target: "[data-custom-address]",
       visible: function (el) { return el.value === el.dataset.customMode; }
     },
+    {
+      match: "select[data-ratelimit-mode]",
+      target: "[data-manual-fields]",
+      visible: function (el) { return el.value === "manual"; }
+    },
+    {
+      match: "select[data-ratelimit-mode]",
+      target: "[data-auto-fields]",
+      visible: function (el) { return el.value === "auto"; }
+    },
     {
       match: "select[data-global-role]",
       target: "[data-domain-pick]",