Switch to phone auth via Twilio SMS and add feature flag system

Replace email-based auth (Resend) with phone-based auth (Twilio SMS).
Add BBQ_FEATURES env var for toggling features at deploy time — when
auth is disabled, no login routes are registered and the app works
as before.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/dashboard.html

@@ -0,0 +1,37 @@
+{{template "layout" .}}
+
+{{define "title"}}bbq — my events{{end}}
+
+{{define "content"}}
+<div class="event-header">
+  <div class="event-tag">Dashboard</div>
+  <h1 class="event-title">My events</h1>
+  <p style="font-family:'DM Mono',monospace;font-size:0.8rem;color:#555;margin-top:8px;">
+    Welcome back, {{.User.Name}}.
+  </p>
+</div>
+
+<div style="margin-bottom:24px;">
+  <a href="/" class="btn-claim" style="text-decoration:none;display:inline-block;">+ Create event</a>
+</div>
+
+{{if .Events}}
+<div class="slots-grid">
+  {{range .Events}}
+  <div class="slot-card">
+    <div class="slot-info">
+      <div class="slot-name">{{.Title}}</div>
+      <div style="font-family:'DM Mono',monospace;font-size:0.72rem;color:#555;">
+        {{.Date}} &middot; {{.Time}} &middot; {{.Location}}
+      </div>
+    </div>
+    <div class="slot-right">
+      <a href="/e/{{.Slug}}/admin/{{.AdminToken}}" class="btn-claim" style="text-decoration:none;">Manage</a>
+    </div>
+  </div>
+  {{end}}
+</div>
+{{else}}
+<p class="nobody" style="text-align:center;padding:40px 0;">No events yet. Create one above!</p>
+{{end}}
+{{end}}

templates/event.html

@@ -49,7 +49,7 @@
         hx-on::after-request="if(event.detail.successful) this.reset()">
     <div class="form-row">
       <label>Your name</label>
-      <input type="text" name="name" placeholder="e.g. Sam" required>
+      <input type="text" name="name" placeholder="e.g. Sam" required value="{{if .User}}{{.User.Name}}{{end}}">
     </div>
     <div class="form-row">
       <label>Note (optional)</label>
@@ -70,7 +70,7 @@
         hx-on::after-request="if(event.detail.successful) this.reset()">
     <div class="form-row">
       <label>Your name</label>
-      <input type="text" name="name" placeholder="e.g. Sam" required>
+      <input type="text" name="name" placeholder="e.g. Sam" required value="{{if .User}}{{.User.Name}}{{end}}">
     </div>
     <div class="form-row">
       <label>Slot</label>

templates/layout.html

@@ -386,6 +386,9 @@
 {{block "admin-bar" .}}{{end}}
 <header>
   <a class="logo" href="/"><span>&#127834;</span> bbq</a>
+  <nav style="font-family:'DM Mono',monospace;font-size:0.75rem;">
+    {{if .User}}<a href="/dashboard" style="color:var(--ink);text-decoration:none;margin-right:12px;">{{.User.Name}}</a><form method="POST" action="/logout" style="display:inline;"><button type="submit" style="background:none;border:none;font-family:inherit;font-size:inherit;cursor:pointer;text-decoration:underline;">log out</button></form>{{else if .AuthEnabled}}<a href="/login" style="color:var(--ink);text-decoration:underline;">log in</a>{{end}}
+  </nav>
 </header>
 <main>
 {{block "content" .}}{{end}}

templates/login.html

@@ -0,0 +1,42 @@
+{{template "layout" .}}
+
+{{define "title"}}bbq — log in{{end}}
+
+{{define "content"}}
+<div class="event-header">
+  <div class="event-tag">Account</div>
+  <h1 class="event-title">Log in</h1>
+  <p style="font-family:'DM Mono',monospace;font-size:0.8rem;color:#555;margin-top:8px;">
+    Enter your phone number to receive a login code.
+  </p>
+</div>
+
+<div class="claim-form-wrapper">
+  {{if eq .Step "phone"}}
+  <form method="POST" action="/login">
+    <div class="form-row">
+      <label>Phone</label>
+      <input type="tel" name="phone" placeholder="(555) 123-4567" required autofocus>
+    </div>
+    <button class="btn-submit" type="submit">Send code &#8599;</button>
+  </form>
+  {{else}}
+  <form method="POST" action="/login/verify">
+    <input type="hidden" name="phone" value="{{.Phone}}">
+    <p style="font-family:'DM Mono',monospace;font-size:0.78rem;color:#555;margin-bottom:16px;">
+      Code sent to <strong>{{.Phone}}</strong>
+    </p>
+    {{if .Error}}
+    <p style="color:#c44;font-size:0.85rem;margin-bottom:12px;">{{.Error}}</p>
+    {{end}}
+    <div class="form-row">
+      <label>6-digit code</label>
+      <input type="text" name="code" placeholder="000000" required autofocus
+             inputmode="numeric" pattern="[0-9]{6}" maxlength="6"
+             style="font-family:'DM Mono',monospace;font-size:1.5rem;letter-spacing:8px;text-align:center;">
+    </div>
+    <button class="btn-submit" type="submit">Verify &#8599;</button>
+  </form>
+  {{end}}
+</div>
+{{end}}

templates/name.html

@@ -0,0 +1,24 @@
+{{template "layout" .}}
+
+{{define "title"}}bbq — your name{{end}}
+
+{{define "content"}}
+<div class="event-header">
+  <div class="event-tag">Account</div>
+  <h1 class="event-title">What's your name?</h1>
+  <p style="font-family:'DM Mono',monospace;font-size:0.8rem;color:#555;margin-top:8px;">
+    This will be used to autofill your name when you RSVP or claim a slot.
+  </p>
+</div>
+
+<div class="claim-form-wrapper">
+  <form method="POST" action="/account/name">
+    <div class="form-row">
+      <label>Name</label>
+      <input type="text" name="name" placeholder="Your name" required autofocus
+             value="{{if .User}}{{.User.Name}}{{end}}">
+    </div>
+    <button class="btn-submit" type="submit">Save &#8599;</button>
+  </form>
+</div>
+{{end}}