feat: DNS provider abstraction — Technitium, Cloudflare, RFC 2136, Manual

- dns-providers/: adapter base class + registry with auto-discovery
- technitium.js: wraps existing Technitium API calls into adapter interface
- cloudflare.js: Cloudflare API v4 adapter (zones, records, credentials)
- rfc2136.js: RFC 2136 dynamic DNS via nsupdate (BIND, PowerDNS, etc.)
- manual.js: no-op adapter for external DNS management with instructions
- provider-dns.js: provider-aware DNS context, resolves active adapter from config
- Universal helper methods: universalCreateRecord/Delete/ResolveRecord
- All 7 route files updated to use universal methods instead of raw dns.call()
- Setup wizard: provider dropdown (Technitium, Cloudflare, RFC 2136, Manual)
- DNS template selector: added Cloudflare and External/Manual options
- Config schema: validates dns.provider field
- Capability gating on Technitium-specific endpoints (logs, restart, update)
- Backward compatible: no provider set = auto-detect (technitium if dns.ip exists)

dashcaddy-api/routes/services.js

@@ -520,9 +520,8 @@ module.exports = function({
 
     if (oldSubdomain !== newSubdomain) {
       try {
-        const dnsToken = dns.getToken();
-        await dns.call(siteConfig.dnsServerIp, '/api/zones/records/delete', { token: dnsToken, domain: oldDomain, type: 'A' });
-        await dns.createRecord(newSubdomain, ip || 'localhost');
+        await dns.universalDeleteRecord(oldDomain);
+        await dns.universalCreateRecord(newSubdomain, ip || 'localhost');
         results.dns = 'updated';
       } catch (e) {
         results.dns = `failed: ${e.message}`;