fix post-login blank page + rebrand login hero

- nginx: use alias for BASE_PATH fallback so static assets resolve
  correctly when deployed under a sub-path (fixes white page on K8s)
- base.html: remove dead template refs (chat, notes, projects) that
  caused html/template to fail silently with Content-Length: 0
- login hero: rebrand from "Chat Switchboard" to "Switchboard Core",
  update tagline and feature pills to reflect platform pivot

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/js/sw/surfaces/login/hero.js

@@ -9,12 +9,12 @@
 const { html } = window;
 
 const PILLS = [
-    { icon: '\u{1F916}', label: 'Multi-Provider AI',    cls: 'ac' },
-    { icon: '\u{1F511}', label: 'Bring Your Own Key',   cls: 'pu' },
-    { icon: '\u{1F465}', label: 'Teams & Projects',     cls: 'ac' },
     { icon: '\u{1F9E9}', label: 'Extensions',           cls: 'pu' },
-    { icon: '\u{1F50D}', label: 'Web Search Tools',     cls: 'ac' },
-    { icon: '\u{1F4DD}', label: 'Notes & Memory',       cls: 'pu' },
+    { icon: '\u{1F310}', label: 'Surfaces',             cls: 'ac' },
+    { icon: '\u{1F465}', label: 'Teams & RBAC',         cls: 'pu' },
+    { icon: '\u{1F517}', label: 'Connections',           cls: 'ac' },
+    { icon: '\u{2699}\u{FE0F}', label: 'Workflows',     cls: 'pu' },
+    { icon: '\u{1F4E6}', label: 'Package Registry',     cls: 'ac' },
 ];
 
 export function Hero({ base = '', version = '', env = null }) {
@@ -28,15 +28,15 @@ export function Hero({ base = '', version = '', env = null }) {
                          src="${base}/favicon.svg?v=${version}"
                          alt="Switchboard Core" />
                     <span class="login-hero-brand-text">
-                        Chat <span class="hl">Switchboard</span>
+                        Switchboard <span class="hl">Core</span>
                     </span>
                 </div>
                 <h1 class="login-anim login-anim-2">
-                    Your AI conversations,${html`<br />`}your infrastructure
+                    Your platform,${html`<br />`}your infrastructure
                 </h1>
                 <p class="login-hero-sub login-anim login-anim-3">
-                    Self-hosted multi-provider chat with team collaboration,
-                    BYOK privacy, and an extensible plugin system.
+                    Self-hosted extensible platform with surfaces, packages,
+                    team RBAC, and a workflow engine.
                 </p>
                 <div class="login-hero-pills login-anim login-anim-4">
                     ${PILLS.map(p => html`