feat(api): add API documentation and ShareX integration

- Add an API documentation page with curl and ShareX examples.
- Implement a dynamic ShareX configuration endpoint (`/api/v1/sharex/warpbox-anonymous.sxcu`) that generates a `.sxcu` file pre-configured with the instance's base URL.
- Update anonymous uploads to return a private management link (`manageUrl`) and a deletion link (`deleteUrl`) in JSON responses.
- Update README with details on Stage 3 Anonymous Integrations.
- Add styling for the new API documentation view and management details.

backend/templates/pages/api.html

@@ -0,0 +1,96 @@
+{{define "api.html"}}{{template "base" .}}{{end}}
+
+{{define "content"}}
+<section class="docs-view" aria-labelledby="api-title">
+  <div class="docs-header">
+    <p class="kicker">Developer docs</p>
+    <h1 id="api-title">Warpbox API</h1>
+    <p>Anonymous uploads for curl, scripts, and ShareX. The upload endpoint accepts multipart files and returns either plain text or JSON based on the <code>Accept</code> header.</p>
+  </div>
+
+  <div class="docs-grid">
+    <article class="card docs-card">
+      <div class="card-content">
+        <h2>Endpoints</h2>
+        <dl class="endpoint-list">
+          <div><dt>Upload</dt><dd><code>POST /api/v1/upload</code></dd></div>
+          <div><dt>Health</dt><dd><code>GET /api/v1/health</code></dd></div>
+          <div><dt>Request schema</dt><dd><a href="/api/v1/schemas/upload-request.json"><code>/api/v1/schemas/upload-request.json</code></a></dd></div>
+          <div><dt>Response schema</dt><dd><a href="/api/v1/schemas/upload-response.json"><code>/api/v1/schemas/upload-response.json</code></a></dd></div>
+        </dl>
+      </div>
+    </article>
+
+    <article class="card docs-card">
+      <div class="card-content">
+        <h2>Curl upload</h2>
+        <p>Without a JSON <code>Accept</code> header, Warpbox prints one plain box URL for shell-friendly usage.</p>
+        <pre><code>curl -F file=@./report.pdf {{.Data.UploadURL}}</code></pre>
+        <p>For automation, request JSON to get file URLs and the private manage/delete URLs.</p>
+        <pre><code>curl -F file=@./report.pdf \
+  -H 'Accept: application/json' \
+  {{.Data.UploadURL}}</code></pre>
+      </div>
+    </article>
+
+    <article class="card docs-card">
+      <div class="card-content">
+        <h2>JSON response</h2>
+        <p>The raw delete token is returned only once inside <code>manageUrl</code> and <code>deleteUrl</code>. Keep those links private.</p>
+        <pre><code>{
+  "boxId": "abc123",
+  "boxUrl": "{{.Data.BaseURL}}/d/abc123",
+  "zipUrl": "{{.Data.BaseURL}}/d/abc123/zip",
+  "manageUrl": "{{.Data.BaseURL}}/d/abc123/manage/private-token",
+  "deleteUrl": "{{.Data.BaseURL}}/d/abc123/manage/private-token/delete",
+  "expiresAt": "2026-06-05T12:00:00Z",
+  "files": [
+    {
+      "id": "file123",
+      "name": "report.pdf",
+      "size": "2.4 MiB",
+      "url": "{{.Data.BaseURL}}/d/abc123/f/file123"
+    }
+  ]
+}</code></pre>
+      </div>
+    </article>
+
+    <article class="card docs-card">
+      <div class="card-content">
+        <h2>ShareX setup</h2>
+        <ol class="docs-steps">
+          <li>Download the instance config: <a href="/api/v1/sharex/warpbox-anonymous.sxcu"><code>/api/v1/sharex/warpbox-anonymous.sxcu</code></a>.</li>
+          <li>Or open the tracked template at <code>{{.Data.ShareXExamplePath}}</code> and change <code>RequestURL</code> to <code>{{.Data.ShareXExampleURL}}</code>.</li>
+          <li>Keep <code>FileFormName</code> as <code>{{.Data.ShareXFileFieldName}}</code>.</li>
+          <li>Import the <code>.sxcu</code> file into ShareX as a custom uploader.</li>
+          <li>Upload a file. ShareX will use <code>boxUrl</code> as the public URL and <code>manageUrl</code> as the deletion URL.</li>
+        </ol>
+        <pre><code>{
+  "RequestMethod": "POST",
+  "RequestURL": "{{.Data.ShareXExampleURL}}",
+  "Headers": { "Accept": "application/json" },
+  "Body": "MultipartFormData",
+  "FileFormName": "{{.Data.ShareXFileFieldName}}",
+  "URL": "$json:boxUrl$",
+  "DeletionURL": "$json:manageUrl$"
+}</code></pre>
+      </div>
+    </article>
+
+    <article class="card docs-card docs-card-wide">
+      <div class="card-content">
+        <h2>Multipart fields</h2>
+        <div class="field-grid">
+          <span><code>file</code></span><p>One or more files for curl, browser, and generic multipart clients.</p>
+          <span><code>sharex</code></span><p>One or more files from ShareX custom uploader configs.</p>
+          <span><code>max_days</code></span><p>Optional number of days before expiration. Defaults to 7.</p>
+          <span><code>max_downloads</code></span><p>Optional download count limit.</p>
+          <span><code>password</code></span><p>Optional password required before viewing/downloading.</p>
+          <span><code>obfuscate_metadata</code></span><p>Optional <code>on</code>; hides names/counts until unlock when a password is set.</p>
+        </div>
+      </div>
+    </article>
+  </div>
+</section>
+{{end}}

backend/templates/pages/home.html

@@ -80,6 +80,10 @@
         </div>
       </div>
       <div class="result-list" id="result-list"></div>
+      <p class="manage-link" id="manage-link" hidden>
+        <span>Keep this private:</span>
+        <a href="/" target="_blank" rel="noopener noreferrer">Manage or delete this upload</a>
+      </p>
     </div>
   </section>
 </section>

backend/templates/pages/manage.html

@@ -0,0 +1,32 @@
+{{define "manage.html"}}{{template "base" .}}{{end}}
+
+{{define "content"}}
+<section class="download-view" aria-labelledby="manage-title">
+  <div class="card download-card">
+    <div class="card-content">
+      <div class="file-emblem" aria-hidden="true">
+        <svg viewBox="0 0 24 24" role="img" focusable="false"><path d="M3 6h18" /><path d="M8 6V4h8v2" /><path d="M19 6l-1 14H6L5 6" /><path d="M10 11v5" /><path d="M14 11v5" /></svg>
+      </div>
+      <h1 id="manage-title">Manage upload</h1>
+      <p class="download-subtitle">This private link can delete the entire box.</p>
+
+      <dl class="manage-details">
+        <div><dt>Box</dt><dd><code>{{.Data.Box.ID}}</code></dd></div>
+        <div><dt>Files</dt><dd>{{.Data.FileCount}}</dd></div>
+        <div><dt>Total size</dt><dd>{{.Data.TotalSize}}</dd></div>
+        <div><dt>Expires</dt><dd>{{.Data.ExpiresLabel}}</dd></div>
+        <div><dt>Downloads</dt><dd>{{.Data.DownloadCount}}{{if .Data.MaxDownloads}} / {{.Data.MaxDownloads}}{{end}}</dd></div>
+        <div><dt>Protected</dt><dd>{{if .Data.Protected}}Yes{{else}}No{{end}}</dd></div>
+      </dl>
+
+      <form action="{{.Data.DeleteActionURL}}" method="post">
+        <button class="button button-danger button-wide" type="submit">
+          <svg viewBox="0 0 24 24" role="img" focusable="false" aria-hidden="true"><path d="M3 6h18" /><path d="M8 6V4h8v2" /><path d="M19 6l-1 14H6L5 6" /></svg>
+          Delete upload
+        </button>
+      </form>
+      <a class="button button-outline button-wide" href="/d/{{.Data.Box.ID}}">Back to box</a>
+    </div>
+  </div>
+</section>
+{{end}}

backend/templates/pages/manage_deleted.html

@@ -0,0 +1,16 @@
+{{define "manage_deleted.html"}}{{template "base" .}}{{end}}
+
+{{define "content"}}
+<section class="download-view" aria-labelledby="deleted-title">
+  <div class="card download-card">
+    <div class="card-content">
+      <div class="file-emblem" aria-hidden="true">
+        <svg viewBox="0 0 24 24" role="img" focusable="false"><path d="M20 6 9 17l-5-5" /></svg>
+      </div>
+      <h1 id="deleted-title">Upload deleted</h1>
+      <p class="download-subtitle">Box <code>{{.Data.ID}}</code> and all of its files have been removed.</p>
+      <a class="button button-primary button-wide" href="/">Upload another file</a>
+    </div>
+  </div>
+</section>
+{{end}}