refactor: full codebase overhaul — dead code removal, env validation, logger migration, date consolidation, Prisma schema cleanup, button consistency, useEffect deps, test coverage

- env.ts: added 10 missing Zod-validated env vars (imager, paypal currency, argon2/bcrypt params)
- Migrated 6 modules from process.env to validated env.* (auth, proxy-auth, paypal, password, redis, imager, moderation, alert, logger)
- Replaced console.warn/error with pino logger in 9 server-side modules
- Removed 50+ dead exports (SWF wrappers, coalesceHotelName, signIn, isStaff re-export, formatTimestamp, Skeleton/SkeletonCard, 4 unused housekeeping sections)
- Consolidated date formatting: 28 files migrated to shared formatDate() from @/lib/format-date
- Wired 4 radio/settings API routes through cached siteSettings service instead of raw Prisma queries
- Added getMany()/getAll() helpers to SiteSettings service
- Removed 88 dead Prisma model definitions (schema 2763→1846 lines)
- Created admin action-helper.ts with wrapAction() for standardized error handling
- Fixed useEffect dependency arrays in 4 data-heavy components
- Replaced raw btn CSS classes with shadcn Button component across admin pages
- Stripped dead i18n namespaces (common, pages.client) from all 22 translation files
- Removed 2 dead scripts (create-release.sh, check-local-imports.ts)
- Fixed knip.json configuration
- Added 7 new test suites: format-date, paypal, moderation, alert, webhook, action-helper, and fixed password.test.ts for env mocking
- All 358 tests passing across 72 test files
- TypeScript: 0 errors

src/app/admin/vpn/page.tsx

@@ -2,6 +2,7 @@ import Link from "next/link";
 import { getTranslations } from "next-intl/server";
 import { saveVpn } from "@/actions/admin-vpn";
 import { StatusCard } from "@/components/admin/dashboard";
+import { Button } from "@/components/ui/button";
 import { siteSettings } from "@/lib/services/site-settings";
 import { redirect } from "next/navigation";
 import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
@@ -164,9 +165,9 @@ export default async function AdminVpn({
 							justifyContent: "flex-end",
 						}}
 					>
-						<button type="submit" className="btn btn-primary">
+						<Button type="submit" variant="default">
 							{t("save")}
-						</button>
+						</Button>
 					</div>
 				</form>
 			</section>
@@ -178,9 +179,11 @@ export default async function AdminVpn({
 						ipLink: (chunks) => <Link href="/admin/ip">{chunks}</Link>,
 					})}
 				</p>
-				<Link href="/admin/ip" className="btn btn-secondary">
-					{t("openIpManagement")}
-				</Link>
+				<Button variant="secondary" asChild>
+					<Link href="/admin/ip">
+						{t("openIpManagement")}
+					</Link>
+				</Button>
 			</section>
 		</main>
 	);