Remove Discord and Google OAuth verification from CMS

- Remove Discord + Google OAuth providers from NextAuth config
- Remove social login buttons (Discord/Google) from login form
- Delete link-discord.ts action and discord-verify-form.tsx component
- Simplify verify page to email-only verification flow
- Remove connections settings page and its link from settings
- Clean env.ts, .env, .env.example of Discord/Google client vars
- Remove discordUrl social icon from register, login, and homepage
- Clean translation files: remove continueWithDiscord, continueWithGoogle, connections keys

src/components/auth/register-form.tsx

@@ -166,12 +166,7 @@ export function RegisterForm({
 								borderColor: "color-mix(in srgb, var(--color-text-muted) 25%, transparent)",
 							}}
 						/>
-						<p
-							className="text-xs mt-1"
-							style={{ color: "var(--color-text-muted)" }}
-						>
-							Geen e-mail? Je kunt later via Discord verifiëren.
-						</p>
+
 					</div>
 				</div>