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/templates.js

@@ -107,10 +107,8 @@ module.exports = function({
     if (oldSubdomain && ctx.dns.getToken()) {
       try {
         const oldDomain = oldSubdomain.includes('.') ? oldSubdomain : ctx.buildDomain(oldSubdomain);
-        const result = await ctx.dns.call(ctx.siteConfig.dnsServerIp, '/api/zones/records/delete', {
-          token: ctx.dns.getToken(), domain: oldDomain, type: 'A', ipAddress: ip || 'localhost'
-        });
-        results.oldDns = result.status === 'ok' ? 'deleted' : result.errorMessage;
+        await ctx.dns.universalDeleteRecord(oldDomain, ip || 'localhost');
+        results.oldDns = 'deleted';
         log.info('dns', 'Old DNS record deleted', { domain: oldDomain });
       } catch (error) {
         results.oldDns = `failed: ${error.message}`;
@@ -120,7 +118,7 @@ module.exports = function({
 
     if (newSubdomain && ctx.dns.getToken()) {
       try {
-        await ctx.dns.createRecord(newSubdomain, ip || 'localhost');
+        await ctx.dns.universalCreateRecord(newSubdomain, ip || 'localhost');
         results.newDns = 'created';
         log.info('dns', 'New DNS record created', { domain: ctx.buildDomain(newSubdomain) });
       } catch (error) {