feat: add PowerDNS reverse DNS (PTR) integration

Introduces an opt-in reverse DNS management subsystem backed by a PowerDNS
Authoritative HTTP API. Runs via a companion WHMCS addon module
(modules/addons/VirtFusionDns) that holds settings and a Test Connection
page; the server module reads those settings from tbladdonmodules and
short-circuits when the addon is absent or disabled, so provisioning is
unaffected for operators who don't use the feature.

Lifecycle hooks:
- createAccount creates PTRs for every assigned IP (forward DNS must
  already resolve to the IP — FCrDNS enforcement)
- renameServer updates only PTRs whose content matched the old hostname,
  preserving client-custom records
- terminateAccount deletes all PTRs before the local state is purged
- TestConnection merges PowerDNS health check with the existing VirtFusion
  check
- A DailyCronJob hook reconciles missing PTRs additive-only (never
  overwrites)

Client UI: new "Reverse DNS" panel on the service overview with one
editable PTR input per assigned IP, per-row status badges, and
forward-DNS rejection on save. Admin services tab gets a parallel
widget with Reconcile (additive) and Reconcile (force reset) buttons.

New subsystem at lib/PowerDns/:
- Client.php    PowerDNS API wrapper (X-API-Key, listZones/getZone/
                patchRRset/notifyZone), auto-NOTIFY on successful PATCH
- Config.php    Loads + decrypts addon settings from tbladdonmodules
- IpUtil.php    PTR-name generation (IPv4 + IPv6), zone matching,
                RFC 2317 classless parsing
- Resolver.php  FCrDNS verification via dns_get_record with CNAME-chain
                following and per-(hostname,ip) caching
- PtrManager.php Orchestrator: syncServer, deleteForServer, listPtrs,
                setPtr, reconcile, reconcileAll

Security hardening helpers added to Module and applied to the rDNS
endpoints:
- requirePost()           HTTP method gate (405 on non-POST mutations)
- requireSameOrigin()     Origin/Referer check against WHMCS host (CSRF
                          defence against cross-site form POST)
- requireServiceStatus()  tblhosting.domainstatus filter (Active for
                          writes, Active+Suspended for reads)

RFC 2317 classless delegations (e.g. 64/64.113.0.203.in-addr.arpa.)
supported with alignment validation: rejects misaligned start addresses
that don't correspond to any real delegation boundary.

PowerDNS zone IDs containing '/' are URL-encoded as '=2F' per the
PowerDNS API convention. PATCH success triggers PUT /zones/{id}/notify
so slaves pick up the SOA-bumped serial immediately.

Includes IPv4 + IPv6 support, per-IP write rate limit (10s), fresh
IP-ownership re-verification on every client write (defends against
stale-ownership after IP reassignment), and audit logging of every
successful edit to the WHMCS module log.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

modules/servers/VirtFusionDirect/templates/overview.tpl

@@ -237,6 +237,28 @@
     </div>
 </div>
 
+{if $rdnsEnabled}
+{* Reverse DNS Panel *}
+<div class="panel card panel-default mb-3">
+    <div class="panel-heading card-header">
+        <h3 class="panel-title card-title m-0">Reverse DNS</h3>
+    </div>
+    <div class="panel-body card-body p-4">
+        <p class="vf-small text-muted mb-3">Set a custom PTR record for each assigned IP. Forward DNS (A/AAAA) for the hostname must already resolve to the IP before the PTR can be saved.</p>
+        <div id="vf-rdns-alert" class="alert" style="display:none;"></div>
+        <div id="vf-rdns-list">
+            <div class="vf-skeleton vf-skeleton-line vf-skeleton-line-medium"></div>
+            <div class="vf-skeleton vf-skeleton-line vf-skeleton-line-medium"></div>
+        </div>
+        <script>
+        if (typeof vfLoadRdns === 'function') {
+            vfLoadRdns('{$serviceid}', '{$systemURL}');
+        }
+        </script>
+    </div>
+</div>
+{/if}
+
 {* Resources Panel — populated by JS after server data loads *}
 <div id="vf-resources-panel" class="panel card panel-default mb-3" style="display: none;">
     <div class="panel-heading card-header">