feat(onboarding): add one-shot bootstrap and first-run setup wizard (#285)

Adds a bootstrap launcher and a blocking first-run onboarding wizard that guides
new users through minimum Hermes setup from the browser UI.

Supported provider flows: OpenRouter, Anthropic, OpenAI, custom OpenAI-compatible.
OAuth/terminal-first flows remain via 'hermes model'.

Security hardening applied during review:
- /api/onboarding/setup restricted to loopback when auth disabled
- Newline injection guard in _write_env_file
- esc() on setup.unsupported_note in onboarding.js
- Test isolation fix (send_key instead of bot_name in contamination test)
- Skip markers for PyYAML-dependent tests in agent-less environments

Tests: 693 passed (up from 679)

Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>
Co-authored-by: gabogabucho <gabogabucho@gmail.com>

static/index.html

@@ -347,6 +347,26 @@
     </div>
   </aside>
 </div>
+<div class="onboarding-overlay" id="onboardingOverlay" style="display:none" role="dialog" aria-modal="true" aria-labelledby="onboardingTitle">
+  <div class="onboarding-card">
+    <div class="onboarding-shell">
+      <div class="onboarding-sidebar">
+        <div class="onboarding-badge" data-i18n="onboarding_badge">FIRST RUN</div>
+        <h2 id="onboardingTitle" data-i18n="onboarding_title">Welcome to Hermes Web UI</h2>
+        <p id="onboardingLead" data-i18n="onboarding_lead">A quick guided setup will check your Hermes install, choose a workspace and model, and optionally protect the app with a password.</p>
+        <div class="onboarding-steps" id="onboardingSteps"></div>
+      </div>
+      <div class="onboarding-main">
+        <div class="onboarding-status" id="onboardingNotice"></div>
+        <div class="onboarding-body" id="onboardingBody"></div>
+        <div class="onboarding-actions">
+          <button class="sm-btn" id="onboardingBackBtn" onclick="prevOnboardingStep()" style="display:none" data-i18n="onboarding_back">Back</button>
+          <button class="sm-btn" id="onboardingNextBtn" onclick="nextOnboardingStep()" style="font-weight:700;color:var(--blue);border-color:rgba(124,185,255,.32)" data-i18n="onboarding_continue">Continue</button>
+        </div>
+      </div>
+    </div>
+  </div>
+</div>
 <div class="settings-overlay" id="settingsOverlay" style="display:none">
   <div class="settings-panel">
     <div class="settings-header">
@@ -471,6 +491,7 @@
 <script src="/static/commands.js"></script>
 <script src="/static/messages.js"></script>
 <script src="/static/panels.js"></script>
+<script src="/static/onboarding.js"></script>
 <script src="/static/boot.js"></script>
 <div class="app-dialog-overlay" id="appDialogOverlay" style="display:none" aria-hidden="true">
   <div class="app-dialog" id="appDialog" role="dialog" aria-modal="true" aria-labelledby="appDialogTitle" aria-describedby="appDialogDesc">