phase 0 complete: turnover doc, roadmap + changelog updated

Phase 0 (Steps 1-10) is done. Codebase gutted from ~800 files/100K+
lines to 462 files/75K lines. K8s deploy live, CI green, login→admin
verified. Main should be protected — all future work via PRs.

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

CHANGELOG.md

@@ -30,6 +30,13 @@ Forked from chat-switchboard v0.38.5. Gutted to a pure extension platform.
 - CI deploy: image var (`BE_IMAGE` → `IMAGE`) — caused `InvalidImageName` in pods
 - CI rollout: deployment name (`switchboard` → `switchboard-be`) — rollout
   verification was looking for wrong deployment name
+- Nginx BASE_PATH: regex cache-header locations intercepted static asset
+  requests before alias could strip the sub-path prefix — moved inside alias block
+- Post-login blank page: dead Go template references (`surface-chat`,
+  `surface-notes`, `surface-projects`) caused html/template to silently
+  produce Content-Length: 0 responses
+- Login branding: "Chat Switchboard" → "Switchboard Core", updated tagline
+  and feature pills to reflect platform pivot
 
 ### Changed