cf-removal: patch registry, pipeline, settings, admin-page, interface

Wires out the Cloudflare Workers AI image provider across the plugin:

- class-image-pipeline.php: drop 'cloudflare' dispatch branch; Runware
  becomes the unrecognised-provider fallback
- class-image-model-registry.php: remove flux-1-schnell/cloudflare row;
  update provider-enum docblocks (runware|openrouter only)
- class-settings-fields-extended.php: remove three CF fields
  (cloudflare_ai_token, cloudflare_account_id, cf_image_via_gateway);
  drop Cloudflare mention from model-picker + NSFW retry descriptions
- class-admin-page.php: remove prautoblogger_cloudflare_ai_token from
  the encrypted-options list
- interface-image-provider.php: retarget preamble @see at Runware +
  OpenRouter; update get_provider_name() example
- class-image-nsfw-blocked.php: generalise preamble (Runware +
  OpenRouter can raise this)

Also cleans stale CF Workers AI mentions in:
class-ajax-handlers.php, interface-model-registry.php,
class-image-nsfw-retry.php, class-open-router-image-pricing.php,
prautoblogger.php.

The Cloudflare AI Gateway path (in class-open-router-config.php,
class-settings-fields.php 'prautoblogger_ai_gateway_base_url',
class-open-router-request-builder.php cache headers) is intentionally
untouched — it fronts OpenRouter and is unrelated to the CF Workers AI
image provider.

includes/providers/class-open-router-image-pricing.php

@@ -4,7 +4,7 @@ declare(strict_types=1);
 /**
  * Pricing + model-id resolution helpers for the OpenRouter image provider.
  *
- * Mirrors the Cloudflare pricing helper pattern. Each model's cost per image
+ * Mirrors the Runware pricing helper pattern. Each model's cost per image
  * is a flat rate sourced from OpenRouter's pricing page (April 2026).
  *
  * Triggered by: PRAutoBlogger_OpenRouter_Image_Provider (both generate_image()
@@ -12,7 +12,7 @@ declare(strict_types=1);
  * Dependencies: None — pure calculation + option reads.
  *
  * @see class-openrouter-image-provider.php — Caller.
- * @see class-cloudflare-image-pricing.php  — Sibling pattern for Cloudflare.
+ * @see class-runware-image-pricing.php     — Sibling pattern for Runware.
  */
 class PRAutoBlogger_OpenRouter_Image_Pricing {