Split internal/web into subpackages before domain-admin growth.

Lay out view, auth, validate, and handlers under internal/web while keeping
the cmd/panel API unchanged; update roadmap and changelog for web-split closure.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/web/view/templates/deliveries.html

@@ -0,0 +1,31 @@
+{{/* The send log is six columns of addresses, subjects and timestamps, so this
+     page takes the whole column rather than the reading measure (see the "wide"
+     block in layout.html). It is declared per page rather than per page name
+     because how wide a page needs to be is a property of that page, not of the
+     navigation entry several pages share. */}}
+{{define "wide"}}wide{{end}}
+
+{{define "content"}}
+<h1>Deliveries</h1>
+
+<div class="card">
+  <h2>Filter</h2>
+  <form method="get" action="/deliveries">
+    <label for="domain">Domain</label>
+    <select id="domain" name="domain">
+      <option value="">All domains</option>
+      {{range .FilterDomains}}<option value="{{.}}" {{if eq . $.FilterDomain}}selected{{end}}>{{.}}</option>{{end}}
+    </select>
+    <label for="app">Application</label>
+    <select id="app" name="app">
+      <option value="">All applications</option>
+      {{range .FilterApps}}<option value="{{.}}" {{if eq . $.FilterApp}}selected{{end}}>{{.}}</option>{{end}}
+    </select>
+    <button type="submit">Filter</button>
+  </form>
+</div>
+
+<div class="card">
+  {{template "deliveries_rows" .}}
+</div>
+{{end}}