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/app/(site)/settings/page.tsx

@@ -127,19 +127,7 @@ export default async function SettingsPage() {
 					</Link>
 				</ContentCard>
 
-				<ContentCard
-					icon="🔗"
-					title={t("connectionsTitle")}
-					subtitle={t("connectionsSubtitle")}
-				>
-					<p className="muted" style={{ marginTop: 0 }}>
-						{t("connectionsDescription")}
-					</p>
-					<Link href="/settings/connections" className="btn btn-outline">
-						{t("manageConnections")}
-					</Link>
-				</ContentCard>
-			</div>
+				</div>
 		</main>
 	);
 }