fix(backend): fix #16994 by approach 6 (#17005)

* fix(backend): narrow down trustproxy default value and enhance documentation on how to configure it

* Update Changelog

* indent [ci skip]

* Update CHANGELOG.md [ci skip]

* add cloudflare specific example

* Update .config/example.yml

Co-authored-by: anatawa12 <anatawa12@icloud.com>

* fix: productionでIPレートリミットされる際にlocalhostからリクエストが来たらログを残すように

* fix: wrong condition

* fix: use own logger for signin api

* flip configuration

* fix

* fix [ci skip]

* fix: wrong message [ci skip]

* fix: どこがおかしいか明記 [ci skip]

---------

Co-authored-by: anatawa12 <anatawa12@icloud.com>

packages/backend/src/server/ServerService.ts

@@ -75,7 +75,7 @@ export class ServerService implements OnApplicationShutdown {
 	@bindThis
 	public async launch(): Promise<void> {
 		const fastify = Fastify({
-			trustProxy: this.config.trustProxy ?? true,
+			trustProxy: this.config.trustProxy,
 			logger: false,
 		});
 		this.#fastify = fastify;