Hub: accounts, IMVU linking by tagline, proxy sign-in, presence, console

People sign up on the website and link IMVU accounts by putting a code in the account's tagline, which the
hub reads from IMVU's public API (the most recent proof wins; link caps per person). IMVU's age verification
or Access Pass make an account adult. T5DE's proxy signs in with a device code and keeps a WebSocket open,
reporting the IMVU account in use and the community products it wears; /online shows those who opted in.
Moderators get a console: who's online, people, link caps, bans, roles, and the audit log. Tests run the
website and API against an embedded Postgres and a fake IMVU API.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/web/templates/signin.html

@@ -0,0 +1,19 @@
+{{define "title"}}Sign in{{end}}
+{{define "content"}}
+<div class="panel narrow">
+  <h1>Sign in</h1>
+  <p class="muted">to your T5DE account.</p>
+  {{if .Error}}<div class="error">{{.Error}}</div>{{end}}
+  <form method="post" action="/signin">
+    <input type="hidden" name="next" value="{{.Next}}">
+    <label for="username">Username</label>
+    <input type="text" id="username" name="username" value="{{.Username}}" autocomplete="username" required autofocus>
+    <label for="password">Password</label>
+    <input type="password" id="password" name="password" autocomplete="current-password" required>
+    <div class="actions">
+      <button>Sign in</button>
+      <span class="muted small">No account? <a href="/signup">Create one</a></span>
+    </div>
+  </form>
+</div>
+{{end}}