feat(manage): add /manage pages to edit caption and date

/manage lists every photo; /manage/edit/{slug} rewrites the photo's
.toml sidecar, which triggers a rebuild. The pages sit behind the same
htpasswd as /upload and are not linked from the public site.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

templates/manage.html

@@ -0,0 +1,114 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <meta name="robots" content="noindex">
+  <title>Manage — Photo Gallery</title>
+  <link rel="stylesheet" href="{{.FontsURL}}">
+  <link rel="stylesheet" href="/static/style.css">
+  <style>
+    :root { --serif: '{{.SerifFamily}}', Georgia, serif; --mj: '{{.MlFamily}}', sans-serif; }
+    .manage-page {
+      max-width: 720px;
+      margin: 0 auto;
+      padding: 32px 20px;
+    }
+    .manage-page .back-btn {
+      color: var(--fg3);
+      text-decoration: none;
+      font-size: 15px;
+    }
+    .manage-page .back-btn:hover { color: var(--fg); }
+    .manage-page h2 {
+      font-family: var(--serif);
+      font-size: 22px;
+      font-weight: 600;
+      color: var(--fg);
+      margin: 16px 0 6px;
+    }
+    .manage-count {
+      font-size: 12px;
+      color: var(--fg4);
+      font-family: monospace;
+      letter-spacing: 0.04em;
+      margin-bottom: 24px;
+    }
+    .saved {
+      margin-bottom: 20px;
+      font-size: 13px;
+      font-family: monospace;
+      padding: 10px 12px;
+      background: #1d2e1d;
+      color: #b8bb26;
+      border: 1px solid #344d28;
+    }
+    .mlist { list-style: none; }
+    .mrow {
+      display: flex;
+      align-items: center;
+      gap: 16px;
+      padding: 12px 0;
+      border-top: 1px solid var(--line);
+    }
+    .mrow img {
+      width: 72px;
+      height: 72px;
+      object-fit: cover;
+      background: var(--bg0);
+      flex: none;
+    }
+    .minfo { flex: 1; min-width: 0; }
+    .mcaption {
+      font-size: 17px;
+      color: var(--fg);
+      overflow-wrap: anywhere;
+    }
+    .mdate {
+      font-size: 12px;
+      color: var(--fg4);
+      font-family: monospace;
+      margin-top: 4px;
+    }
+    .mactions {
+      flex: none;
+      display: flex;
+      gap: 14px;
+      font-size: 15px;
+    }
+    .mactions a { color: var(--fg3); text-decoration: none; }
+    .mactions a:hover { color: var(--fg); }
+    .mactions .medit { color: var(--aqua); }
+    .mempty { color: var(--fg4); font-size: 15px; }
+  </style>
+</head>
+<body>
+  <div class="manage-page">
+    <a href="/" class="back-btn">← Gallery</a>
+    <h2>Manage photos</h2>
+    <p class="manage-count">{{len .Photos}} {{if eq (len .Photos) 1}}photo{{else}}photos{{end}}</p>
+
+    {{if .Saved}}<p class="saved">✓ saved “{{.Saved}}”</p>{{end}}
+
+    {{if .Photos}}
+    <ul class="mlist">
+      {{range .Photos}}
+      <li class="mrow">
+        <img src="/{{.Thumb}}" alt="" loading="lazy">
+        <div class="minfo">
+          <p class="mcaption">{{.Caption}}</p>
+          <p class="mdate">{{.Date.Format "2006-01-02"}}</p>
+        </div>
+        <div class="mactions">
+          <a href="/photo/{{.Slug}}/">View</a>
+          <a href="/manage/edit/{{.Slug}}" class="medit">Edit</a>
+        </div>
+      </li>
+      {{end}}
+    </ul>
+    {{else}}
+    <p class="mempty">No photos yet.</p>
+    {{end}}
+  </div>
+</body>
+</html>