Add complete alert rule portfolio review

### Problem

The alert rule table is paginated and filtered. Operators can duplicate, import, enable, and disable rules, but they cannot review the complete domain inventory for combinations that create duplicate notifications or silently stop coverage. Problems spanning pages are especially difficult to spot.

### Proposed change

Add a read-only portfolio review for both cluster and business alert domains. It should use the existing complete rule-list contract and identify only evidence-backed conditions:

- enabled rules with identical scope and evaluation signatures;
- duplicate rule names;
- enabled rules without notification channels;
- rules referencing instances that no longer exist;
- scopes for which every remaining rule is disabled.

Different thresholds must not be treated as conflicts. The review should provide issue and rule views, filters, CSV export, Chinese/English copy, and focused tests. It must not mutate rules or depend on the current page/filter state.

Start by tracing the existing complete rule-list contract and the alert rule table's pagination and filtering behavior for cluster and business domains. Define the review's issue and rule views, filters, CSV export, Chinese/English copy, and focused tests; done means read-only, evidence-backed findings across the complete inventory without depending on the current page or filter state.

Written by the indexing model from the issue text.