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/restore.js

@@ -458,7 +458,7 @@ module.exports = function({ docker, caddy, servicesStateManager, asyncHandler, e
     // DNS record
     if (manifest.config.createDns && manifest.caddy.routingMode !== 'subdirectory') {
       try {
-        await ctx.dns.createRecord(manifest.config.subdomain, manifest.config.ip);
+        await ctx.dns.universalCreateRecord(manifest.config.subdomain, manifest.config.ip);
         log.info('restore', 'DNS record recreated', { subdomain: manifest.config.subdomain });
       } catch (e) {
         log.warn('restore', `DNS recreation failed: ${e.message}`);