cf-removal: add v0.10.0 migration + tests

New class PRAutoBlogger_Migrate_Remove_Cloudflare_V0100 (own file so
class-activator.php stays under 300 lines). Runs from
PRAutoBlogger::maybe_run_db_migrations() right after the v0.9.0
migration. Idempotent via prautoblogger_migrated_remove_cloudflare_v0100
flag option (picked up by the uninstall prefix sweep).

Migrates any user on a Cloudflare image provider to Runware FLUX.1
schnell (closest equivalent, ~bash.0006/image). Detects the three
shapes a legacy user can be in: registry-derived provider ===
'cloudflare', image_provider option === 'cloudflare', or the legacy
slug 'flux-1-schnell'.

Cleans up three now-dead options: prautoblogger_cloudflare_ai_token,
prautoblogger_cloudflare_account_id, prautoblogger_cf_image_via_gateway.
Does NOT touch prautoblogger_ai_gateway_base_url — that option is
shared with the OpenRouter AI Gateway route and must stay (live-
verified test).

Tests (tests/unit/Core/ActivatorRemoveCloudflareTest.php):
- cloudflare user → runware schnell
- non-cloudflare user preserved
- runware user preserved
- legacy 'flux-1-schnell' slug triggers migration
- second run is a no-op (does not clobber admin manual changes)
- AI Gateway URL preserved across every path

ImageModelRegistryTest updated: allowed-provider set is now
['runware','openrouter']; new test_cloudflare_entries_removed_v0100
test pins the scope boundary.

includes/class-prautoblogger.php

@@ -220,7 +220,6 @@ class PRAutoBlogger {
 			}
 			update_option( 'prautoblogger_migrated_style_suffix_v3', '1' );
 		}
-
 		// One-time migration (v4): remove caption-in-image instruction from style suffix.
 		// Captions are now inserted as HTML below the image, not baked into the image.
 		if ( ! get_option( 'prautoblogger_migrated_style_suffix_v4' ) ) {
@@ -232,8 +231,9 @@ class PRAutoBlogger {
 			update_option( 'prautoblogger_migrated_style_suffix_v4', '1' );
 		}
 
-		// v0.9.0: flip legacy default image model to Runware schnell.
+		// v0.9.0 — Runware as default image model. v0.10.0 — remove CF Workers AI.
 		PRAutoBlogger_Activator::migrate_default_image_v090();
+		PRAutoBlogger_Migrate_Remove_Cloudflare_V0100::run();
 
 		// One-time migration: re-wrap existing encrypted values with "enc:" prefix.
 		if ( ! get_option( 'prautoblogger_migrated_enc_prefix' ) ) {