step 5 (continued): prune stale root files, drop frontend split

Delete Dockerfile.frontend and docker-entrypoint-fe.sh (single-image
decision per ROADMAP). Remove gutted /chat, /notes, /projects routes
from nginx.conf. Fix Chat Switchboard branding in entrypoint and
.env.example. Update DB names to switchboard_core, remove dead
Extraction config.

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

server/.env.example

@@ -1,4 +1,4 @@
-# Chat Switchboard v0.12 - Server Environment Variables
+# Switchboard Core - Server Environment Variables
 # Copy this file to .env and fill in the values
 
 # ── Server ───────────────────────────────────
@@ -9,15 +9,17 @@ BASE_PATH=                     # e.g. /chat for path-based routing
 # ── Database (PostgreSQL) ────────────────────
 DB_HOST=localhost
 DB_PORT=5432
-DB_USER=chat_switchboard
+DB_USER=switchboard_core
 DB_PASSWORD=your-secure-password-here
-DB_NAME=chat_switchboard
+DB_NAME=switchboard_core
 DB_SSL_MODE=disable
 DB_MAX_CONNS=25
 
 # ── Auth ─────────────────────────────────────
 JWT_SECRET=your-super-secret-jwt-key-change-in-production
-JWT_EXPIRATION=24h
+# JWT durations (hardcoded in handlers/auth.go — not configurable via env):
+#   Access token:  15 minutes
+#   Refresh token: 7 days
 JWT_ISSUER=switchboard-core
 
 # ── Bootstrap Admin ──────────────────────────
@@ -61,7 +63,3 @@ STORAGE_PATH=/data/storage
 # S3_REGION=us-east-1
 # S3_PREFIX=                    # optional key prefix for shared buckets
 # S3_FORCE_PATH_STYLE=true      # required for MinIO, Ceph RGW
-
-# ── Extraction ───────────────────────────────
-# EXTRACTION_MODE=inline        # "inline" or "sidecar"
-# EXTRACTION_CONCURRENCY=3