Name the item and what is lost in each delete prompt (closes #400)

The three delete prompts on the webhook page were generic ("Delete this target?") and named nothing. Each now names the item and says what is lost: for a webhook, its stored events, with their number (the figure the statistics pane shows), and their deliveries, while any archive files it wrote are kept; for an entrypoint, that senders using its URL get an error from now on and the URL cannot be restored; for a target, that nothing more is delivered to it while its past deliveries stay in the event log. They stay the browser's own prompts, and a name's quotes, backslashes, newlines or a closing script tag reach the prompt escaped.

Model: opus-5-5

templates/source_detail.html

@@ -20,7 +20,11 @@
             <div class="flex gap-2">
                 <a href="/hook/{{.Webhook.ID}}/events" class="btn-secondary">Full Event Log</a>
                 <a href="/hook/{{.Webhook.ID}}/edit" class="btn-secondary">Edit</a>
-                <form method="POST" action="/hook/{{.Webhook.ID}}/delete" onsubmit="return confirm('Delete this webhook and all its data?')">
+                <!-- The delete prompts are the browser's own, so they
+                     work without the page's scripts. The template
+                     escapes each name for the script, so a quote or a
+                     backslash in it shows as typed. -->
+                <form method="POST" action="/hook/{{.Webhook.ID}}/delete" onsubmit="return confirm('Delete webhook &quot;{{.Webhook.Name}}&quot;?\n\nThis deletes its stored events{{with .Stats}} ({{.WithinRetention.Events}}){{end}} and their deliveries. Any archive files it wrote are kept.')">
                     <input type="hidden" name="csrf_token" value="{{.CSRFToken}}">
                     <button type="submit" class="btn-danger">Delete</button>
                 </form>
@@ -83,7 +87,7 @@
                                     {{if .Active}}Deactivate{{else}}Activate{{end}}
                                 </button>
                             </form>
-                            <form method="POST" action="/hook/{{$.Webhook.ID}}/entrypoints/{{.ID}}/delete" onsubmit="return confirm('Delete this entrypoint?')" class="inline">
+                            <form method="POST" action="/hook/{{$.Webhook.ID}}/entrypoints/{{.ID}}/delete" onsubmit="return confirm('Delete entrypoint &quot;{{if .Description}}{{.Description}}{{else}}{{$.BaseURL}}/h/{{.Path}}{{end}}&quot;?\n\nSenders using its URL get an error from now on, and the URL cannot be restored.')" class="inline">
                                 <input type="hidden" name="csrf_token" value="{{$.CSRFToken}}">
                                 <button type="submit" class="btn-small text-red-600" title="Delete">Delete</button>
                             </form>
@@ -249,7 +253,7 @@
                                     {{if .Active}}Deactivate{{else}}Activate{{end}}
                                 </button>
                             </form>
-                            <form method="POST" action="/hook/{{$.Webhook.ID}}/targets/{{.ID}}/delete" onsubmit="return confirm('Delete this target?')" class="inline">
+                            <form method="POST" action="/hook/{{$.Webhook.ID}}/targets/{{.ID}}/delete" onsubmit="return confirm('Delete target &quot;{{.Name}}&quot;?\n\nNothing more is delivered to it. Its past deliveries stay in the event log.')" class="inline">
                                 <input type="hidden" name="csrf_token" value="{{$.CSRFToken}}">
                                 <button type="submit" class="btn-small text-red-600" title="Delete">Delete</button>
                             </form>