fix: correct announcement API endpoint and add optional content fields (#20)

## Summary

- Fixes the announcement API URL from `/announcement` to `/api/announcement`
- Adds three optional additional content text inputs (Parts 2–4) to the announcement modal
- The bot concatenates all non-empty content fields with double newlines before forwarding to the API
- Only the first content field and the category selector remain required

## Test Plan

- [ ] Run `/announcement` and verify the modal opens with four content fields and a category selector
- [ ] Submit with only the first content field filled — verify it sends correctly
- [ ] Submit with multiple content fields filled — verify they are concatenated in the API request
- [ ] Verify the API no longer returns HTTP 405

Reviewed-on: #20
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

bot/src/utils/checkEntitlement.ts

@@ -4,7 +4,7 @@
  * @author Naomi Carrigan
  */
 
-import { entitledGuilds, entitledUsers } from "../config/entitlements.js";
+import { entitledGuilds, naomiId } from "../config/entitlements.js";
 import type { Client, Guild, User } from "discord.js";
 
 /**
@@ -17,7 +17,7 @@ const checkUserEntitlement = async(
   hikari: Client,
   user: User,
 ): Promise<boolean> => {
-  if (entitledUsers.includes(user.id)) {
+  if (user.id === naomiId) {
     return true;
   }
   const entitlements = await hikari.application?.entitlements.fetch({