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/src/context/dns.js

@@ -1,8 +1,14 @@
 /**
  * DNS context - Technitium DNS operations and token management
+ * 
+ * DEPRECATED: This module is kept for backward compatibility.
+ * New code should use src/context/provider-dns.js which supports multiple providers.
+ * 
+ * This module now delegates to the provider system internally.
  */
 const { TIMEOUTS, SESSION_TTL, CADDY } = require('../../constants');
 const { createCache, CACHE_CONFIGS } = require('../../cache-config');
+const { createProviderDnsContext } = require('./provider-dns');
 
 // DNS token management
 let dnsToken = process.env.DNS_ADMIN_TOKEN || '';
@@ -281,6 +287,10 @@ function invalidateTokenForServer(serverIp) {
 }
 
 function createDnsContext(siteConfig, buildDomain, credentialManager, fetchT, httpsAgent, log, DNS_CREDENTIALS_FILE) {
+  // Create the new provider-aware context
+  const providerCtx = createProviderDnsContext(siteConfig, buildDomain, credentialManager, fetchT, httpsAgent, log, DNS_CREDENTIALS_FILE);
+
+  // Legacy Technitium-specific wrappers (kept for backward compat)
   const ensureToken = () => ensureValidDnsToken(siteConfig, credentialManager, fetchT, log);
   const require = (providedToken) => requireDnsToken(providedToken, siteConfig, credentialManager, fetchT, log);
   const getForServer = (server, role) => getTokenForServer(server, siteConfig, credentialManager, fetchT, log, role);
@@ -289,6 +299,7 @@ function createDnsContext(siteConfig, buildDomain, credentialManager, fetchT, ht
   const call = (server, apiPath, params) => callDns(server, apiPath, params, fetchT, httpsAgent);
 
   return {
+    // Legacy Technitium-specific interface (unchanged)
     call,
     buildUrl: buildDnsUrl,
     requireToken: require,
@@ -302,6 +313,17 @@ function createDnsContext(siteConfig, buildDomain, credentialManager, fetchT, ht
     invalidateTokenForServer,
     refresh,
     credentialsFile: DNS_CREDENTIALS_FILE,
+
+    // Provider-aware methods (new)
+    getProviderId: providerCtx.getProviderId,
+    getActiveProvider: providerCtx.getActiveProvider,
+    getAvailableProviders: providerCtx.getAvailableProviders,
+    supportsCapability: providerCtx.supportsCapability,
+
+    // Universal DNS helpers (delegated to provider context)
+    universalCreateRecord: providerCtx.universalCreateRecord,
+    universalDeleteRecord: providerCtx.universalDeleteRecord,
+    universalResolveRecord: providerCtx.universalResolveRecord,
   };
 }