fix(operation-trace): repair export URL, drop dead action, prune unused keys

- Export download failed because the URL builder appended the path to a
  "/" base, producing a protocol-relative "//api/..." URL that the browser
  read as host "api"; the request never reached the backend. Resolve the
  base to the current origin, mirroring the other URL builders.
- Remove the orphan ``clear_prune`` action: the branch has no prune/clear
  route and no route rule maps to it, so it could never be produced. Its
  i18n key is removed too.
- Remove ``tamperedCount``, now unreferenced after the verification badge
  was split into integrity/chain counters. The operationTrace catalogue is
  now free of unproduced keys.
- Correct the settings controller docstring: only governance, operation
  logs, filters and export routes exist; there is no on-demand delete.

Verified: no producer for clear_prune, classify() can no longer emit it,
operationTrace orphan scan returns none, tsc/check-i18n/prettier/py_compile
all pass.

web/src/app/infra/http/BackendClient.ts

@@ -1867,12 +1867,19 @@ export class BackendClient extends BaseHttpClient {
       params.set(key, String(value));
     }
     const suffix = params.toString();
-    return `${this.getBaseUrl()}/api/v1/settings/operation-logs/export${
+    // A base of "/" means "same origin". Appending the path directly produced
+    // a protocol-relative "//api/..." URL, which a browser reads as the host
+    // "api" — the export request then never reached the backend. Resolve the
+    // base to the current origin first, mirroring the other URL builders here.
+    const apiBase =
+      this.instance.defaults.baseURL === '/' || !this.instance.defaults.baseURL
+        ? window.location.origin
+        : this.instance.defaults.baseURL.replace(/\/$/, '');
+    return `${apiBase}/api/v1/settings/operation-logs/export${
       suffix ? `?${suffix}` : ''
     }`;
   }
 
-
   public setPassword(
     newPassword: string,
     currentPassword?: string,