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/apps/deploy.js

@@ -316,7 +316,7 @@ module.exports = function({ docker, caddy, credentialManager, servicesStateManag
       let dnsWarning = null;
       if (config.createDns && !isSubdirectoryMode) {
         try {
-          await ctx.dns.createRecord(config.subdomain, config.ip);
+          await ctx.dns.universalCreateRecord(config.subdomain, config.ip);
           log.info('deploy', 'DNS record created', { domain: ctx.buildDomain(config.subdomain), ip: config.ip });
         } catch (dnsError) {
           await logError('app-deploy-dns', dnsError, { appId, subdomain: config.subdomain, ip: config.ip });