[FEATURE] Add IP blocklist with configurable blocking behavior

Add support for an IP blocklist that allows administrators to flag IP addresses and automatically block their requests using configurable responses such as **HTTP 403**, redirect to a custom URL, or silent drop.

### Motivation

This enables proactive mitigation of malicious traffic directly from the plugin dashboard.

### Proposed behavior

* Admin UI to add/remove IPs to blocklist
* Blocking response options:

* HTTP 403
* redirect to custom URL
* silent drop
* Blocklist entries override normal scoring logic

### Acceptance Criteria

* [ ] Admin UI allows adding/removing IPs from blocklist
* [ ] Blocking response type is configurable
* [ ] Requests from blocked IPs are intercepted early
* [ ] Blocked requests are logged
* [ ] Feature documented in settings help text