Add /training page with four self-hosted walkthrough videos

- Videos loudness-normalized to -16 LUFS (originals were ~-33 LUFS).
- Static file serving rewritten to stream with HTTP Range support so
  video seeking works; .mp4/.webm MIME types added.
- Training nav links on homepage and /start, plus a first-time callout
  on /start; training page views tracked per source in admin analytics.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

public/admin.html

@@ -2,7 +2,7 @@
 <section id="loginView" class="login-panel"><div class="brand" style="margin-bottom:22px"><div class="brand-mark">RM</div><span>Crypto Team Build<small>Sponsor Router Admin</small></span></div><h1>Team Admin</h1><p>Manage the current sponsor, qualification queue, and onboarding settings.</p><form id="loginForm"><div class="field"><label for="password">Admin password</label><input id="password" class="input" type="password" autocomplete="current-password" required></div><button class="btn btn-primary" style="width:100%">Sign in</button><div id="loginError" class="micro" style="color:var(--danger)"></div></form></section>
 <section id="adminView" class="admin hidden"><div class="admin-top"><div><div class="eyebrow">Sponsor router</div><h1>Crypto Team Build Admin</h1></div><div class="nav-actions"><a class="btn btn-secondary" href="/start" target="_blank">View Live Page ↗</a><button id="logoutBtn" class="btn btn-secondary">Log out</button></div></div>
 <div class="admin-grid"><div class="stack"><div class="table-card"><div style="display:flex;justify-content:space-between;gap:12px;align-items:center;margin-bottom:12px"><div><h2 style="margin:0">Sponsor Queue</h2><p style="color:var(--muted);margin:4px 0 0;font-size:13px">Mark a sponsor qualified to automatically activate the next waiting position.</p></div></div><div class="table-wrap"><table class="table"><thead><tr><th>Order</th><th>Sponsor</th><th>Parent</th><th>Directs</th><th>Level</th><th>Status</th><th>Clicks</th><th>Actions</th></tr></thead><tbody id="sponsorRows"></tbody></table></div></div>
-<div class="table-card"><div style="margin-bottom:12px"><h2 style="margin:0">Traffic &amp; Conversions</h2><p style="color:var(--muted);margin:4px 0 0;font-size:13px">First-touch source per visitor session (referring domain or utm_source). Funnel: bridge page → start page → join click.</p></div><div id="funnelStats" class="funnel"></div><div class="table-wrap"><table class="table"><thead><tr><th>Source</th><th>Bridge views</th><th>Start views</th><th>Join clicks</th><th>Start → Join</th></tr></thead><tbody id="trafficRows"></tbody></table></div></div></div>
+<div class="table-card"><div style="margin-bottom:12px"><h2 style="margin:0">Traffic &amp; Conversions</h2><p style="color:var(--muted);margin:4px 0 0;font-size:13px">First-touch source per visitor session (referring domain or utm_source). Funnel: bridge page → start page → join click.</p></div><div id="funnelStats" class="funnel"></div><div class="table-wrap"><table class="table"><thead><tr><th>Source</th><th>Bridge views</th><th>Start views</th><th>Training views</th><th>Join clicks</th><th>Start → Join</th></tr></thead><tbody id="trafficRows"></tbody></table></div></div></div>
 <div class="stack"><div class="table-card"><h2 style="margin-top:0">Add Sponsor</h2><form id="addSponsorForm"><div class="form-grid"><div class="field"><label>ID</label><input name="id" class="input" required></div><div class="field"><label>Name</label><input name="name" class="input" required></div><div class="field"><label>Parent ID</label><input name="parentId" class="input"></div><div class="field"><label>Level</label><select name="level" class="select"><option>Scintilla</option><option>Ascensus</option><option>Fabrica</option><option>Culmen</option><option>Apex</option><option>Fastigium</option><option>Vertex</option><option>Corona</option></select></div></div><div class="field"><label>Notes</label><input name="notes" class="input"></div><button class="btn btn-teal" style="width:100%">Add to Queue</button></form></div>
 <div class="table-card"><h2 style="margin-top:0">Public Page Settings</h2><form id="configForm"><div class="field"><label>Site name</label><input name="siteName" class="input"></div><div class="field"><label>Program name</label><input name="programName" class="input"></div><div class="field"><label>Bridge headline</label><input name="bridgeHeadline" class="input"></div><div class="field"><label>Bridge subheadline</label><textarea name="bridgeSubheadline" class="input" rows="3"></textarea></div><div class="field"><label>Premium entry (POL)</label><input name="premiumEntryPol" class="input" type="number"></div><div class="field"><label>RM dApp referral base URL</label><input name="dappReferralBaseUrl" class="input" placeholder="https://app.thermcircle.com?ref="></div><div class="field"><label>Telegram/support URL (optional)</label><input name="telegramUrl" class="input"></div><div class="field"><label>Support message</label><textarea name="supportLabel" class="input" rows="3"></textarea></div><label style="text-transform:none;letter-spacing:0;margin:10px 0"><input type="checkbox" name="showSponsorName"> Show sponsor name publicly</label><label style="text-transform:none;letter-spacing:0;margin:10px 0"><input type="checkbox" name="showQueueProgress"> Show number waiting in queue</label><button class="btn btn-primary" style="width:100%;margin-top:8px">Save Settings</button></form></div></div></div></section>
 <div id="toast" class="toast"></div><script src="/admin.js"></script></body></html>