Add grpcserver test coverage

- Add comprehensive test file for internal/grpcserver package
- Cover interceptors, system, engine, policy, and auth handlers
- Cover pbToRule/ruleToPB conversion helpers
- 37 tests total; CA/PKI/ACME and Login/Logout skipped (require live deps)

Co-authored-by: Junie <junie@jetbrains.com>

web/templates/unseal.html

@@ -1,13 +1,22 @@
 {{define "title"}} - Unseal{{end}}
+{{define "container-class"}}auth-container{{end}}
 {{define "content"}}
-<h2>Unseal Metacrypt</h2>
-<p>The service is sealed. Enter the seal password to unseal.</p>
-{{if .Error}}<div class="error">{{.Error}}</div>{{end}}
-<form method="POST" action="/unseal">
-    <div class="form-group">
-        <label for="password">Seal Password</label>
-        <input type="password" id="password" name="password" required autofocus>
-    </div>
-    <button type="submit">Unseal</button>
-</form>
+<div class="auth-header">
+    <div class="brand">Metacrypt</div>
+    <div class="tagline">Cryptographic Services</div>
+</div>
+<div class="card">
+    <div class="card-title">Unseal</div>
+    <p>The service is sealed. Enter the seal password to restore access.</p>
+    {{if .Error}}<div class="error">{{.Error}}</div>{{end}}
+    <form method="POST" action="/unseal">
+        <div class="form-group">
+            <label for="password">Seal Password</label>
+            <input type="password" id="password" name="password" required autofocus autocomplete="current-password">
+        </div>
+        <div class="form-actions">
+            <button type="submit">Unseal</button>
+        </div>
+    </form>
+</div>
 {{end}}