Keep what was typed when a target or webhook edit is refused (closes #381)

A refused save on the target edit page answered with a bare text page, losing the form and everything typed, and the webhook edit page came back with the stored values instead of the submitted ones. A refused target edit now shows the edit form again with the reason above it and every value submitted, with the same status codes as before; a refused webhook edit keeps the submitted name, description and retention. Target edits use the same validation as new targets, with no second copy; an encoding or database failure stays a logged 500. The browser test covers a refused save on both pages, and its main function is now a plain list of checks.

Model: opus-5-5

templates/target_edit.html

@@ -17,7 +17,7 @@
 
         {{if or (eq .Target.Type "http") (eq .Target.Type "slack")}}
         <div class="mb-6 rounded-md bg-gray-50 p-4 text-sm text-gray-700">
-            This form shows the target's stored destination in full, including any credential carried in its URL or headers. It is the only page that does; everywhere else the value is masked.
+            This form shows the target's destination in full, including any credential carried in its URL or headers. It is the only page that does; everywhere else the value is masked.
         </div>
         {{end}}
 
@@ -26,25 +26,25 @@
 
             <div class="form-group">
                 <label for="name" class="label">Name</label>
-                <input type="text" id="name" name="name" value="{{.Target.Name}}" required class="input">
+                <input type="text" id="name" name="name" value="{{.TargetForm.Name}}" required class="input">
             </div>
 
             {{if eq .Target.Type "http"}}
             <div class="form-group">
                 <label for="url" class="label">Destination URL</label>
-                <input type="url" id="url" name="url" value="{{.Target.Config.URL}}" required class="input">
+                <input type="url" id="url" name="url" value="{{.TargetForm.URL}}" required class="input">
                 <p class="text-xs text-gray-500 mt-1">Revalidated on save; destinations that resolve to private or link-local addresses are rejected.</p>
             </div>
 
             <div class="form-group">
                 <label for="headers" class="label">Headers</label>
-                <textarea id="headers" name="headers" rows="4" class="input" placeholder="Authorization: Bearer ...">{{.Target.Config.Headers}}</textarea>
+                <textarea id="headers" name="headers" rows="4" class="input" placeholder="Authorization: Bearer ...">{{.TargetForm.Headers}}</textarea>
                 <p class="text-xs text-gray-500 mt-1">One <code>Name: value</code> per line, sent with every delivery. Leave blank for none. <code>Host</code>, <code>Content-Length</code>, <code>Transfer-Encoding</code>, <code>Connection</code>, <code>Trailer</code> and <code>User-Agent</code> are set by the delivery engine and are rejected here rather than silently ignored. Headers set here are dropped if a redirect leaves the destination's own origin, so a credential cannot follow one to another host.</p>
             </div>
 
             <div class="form-group">
                 <label for="timeout" class="label">Timeout (seconds)</label>
-                <input type="number" id="timeout" name="timeout" value="{{.Target.Config.Timeout}}" min="0" max="{{.MaxTimeout}}" class="input">
+                <input type="number" id="timeout" name="timeout" value="{{.TargetForm.Timeout}}" min="0" max="{{.MaxTimeout}}" class="input">
                 <p class="text-xs text-gray-500 mt-1">Per-request timeout, at most {{.MaxTimeout}} seconds. Leave blank to use the default.</p>
             </div>
             {{end}}
@@ -52,7 +52,7 @@
             {{if eq .Target.Type "slack"}}
             <div class="form-group">
                 <label for="url" class="label">Webhook URL</label>
-                <input type="url" id="url" name="url" value="{{.Target.Config.URL}}" required class="input">
+                <input type="url" id="url" name="url" value="{{.TargetForm.URL}}" required class="input">
                 <p class="text-xs text-gray-500 mt-1">Slack or Mattermost incoming webhook URL. Revalidated on save.</p>
             </div>
             {{end}}
@@ -60,7 +60,7 @@
             {{if eq .Target.Type "database"}}
             <div class="form-group">
                 <label for="expiry" class="label">Archive Expiry</label>
-                <input type="text" id="expiry" name="expiry" value="{{.Target.Config.Expiry}}" placeholder="never" class="input">
+                <input type="text" id="expiry" name="expiry" value="{{.TargetForm.Expiry}}" placeholder="never" class="input">
                 <p class="text-xs text-gray-500 mt-1">"never" (the default when blank) keeps archived rows forever, or a Go duration like "720h" prunes older rows.</p>
             </div>
             {{end}}
@@ -68,7 +68,7 @@
             {{if or (eq .Target.Type "http") (eq .Target.Type "slack")}}
             <div class="form-group">
                 <label for="max_retries" class="label">Max retries</label>
-                <input type="number" id="max_retries" name="max_retries" value="{{.Target.MaxRetries}}" min="0" max="20" class="input">
+                <input type="number" id="max_retries" name="max_retries" value="{{.TargetForm.MaxRetries}}" min="0" max="20" class="input">
                 <p class="text-xs text-gray-500 mt-1">This is the total number of delivery attempts, not retries on top of the first: a value of 3 makes three attempts in all. 0 means a single attempt with no retries and no circuit breaker.</p>
             </div>
             {{end}}