unify k8s naming: drop be/fe split, single switchboard deployment

- k8s/backend.yaml → k8s/switchboard.yaml (already renamed)
- Deployment/Service name: switchboard-be → switchboard
- Removed component:backend labels (single image, no component split)
- Ingress: all paths route to switchboard service on :8080
- CI: updated manifest render, apply, and rollout references
- Removed stale extractor sidecar and extraction env vars
- Updated CHANGELOG and ROADMAP with CI fixes and design decisions

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

CHANGELOG.md

@@ -23,6 +23,14 @@ Forked from chat-switchboard v0.38.5. Gutted to a pure extension platform.
   filters, retention, workspace
 - **29 handler files**, 6 test files, ~44K lines total
 
+### Fixed
+
+- CI deploy: k8s resource quantity vars (`BE_MEMORY_REQUEST` → `MEMORY_REQUEST`)
+  aligned with CI workflow outputs — `envsubst` was producing empty strings
+- 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
+
 ### Changed
 
 - Module renamed: `chat-switchboard` → `switchboard-core`