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/interface-image-provider.php

@@ -2,7 +2,7 @@
 declare(strict_types=1);
 
 /**
- * Contract for any image generation provider (Cloudflare Workers AI, DALL-E, etc.).
+ * Contract for any image generation provider (Runware FLUX, OpenRouter Gemini, etc.).
  *
  * Consumers depend on this interface, never on a concrete provider — swapping
  * providers means writing one new class, not refactoring the pipeline. This
@@ -13,7 +13,8 @@ declare(strict_types=1);
  *               content generation run, after editorial review, before publish.
  * Dependencies: None at interface level — implementations wrap a specific HTTP API.
  *
- * @see class-cloudflare-image-provider.php — Cloudflare Workers AI implementation.
+ * @see class-runware-image-provider.php    — Runware FLUX implementation (default).
+ * @see class-open-router-image-provider.php — OpenRouter image implementation.
  * @see interface-llm-provider.php          — Parallel pattern for LLM providers.
  * @see ARCHITECTURE.md                     — External API Integrations table.
  */
@@ -79,7 +80,7 @@ interface PRAutoBlogger_Image_Provider_Interface {
 	/**
 	 * Machine-readable provider identifier used in logs and settings.
 	 *
-	 * @return string Lowercase identifier, e.g. 'cloudflare_workers_ai'.
+	 * @return string Lowercase identifier, e.g. 'runware' or 'openrouter'.
 	 */
 	public function get_provider_name(): string;