chore(dev): add docker-compose.dev.yaml and default to same-origin UI

Adds an opt-in compose override that bind-mounts the three_cx provider
files (and the alembic versions dir, so newer local migrations resolve)
into the prebuilt API image — useful when iterating on a provider
without rebuilding. Loaded explicitly via
`docker compose -f docker-compose.yaml -f docker-compose.dev.yaml up`.

Also blanks the default `NEXT_PUBLIC_BACKEND_URL` in `ui/.env.example`
so the browser uses `window.location.origin` and the Next.js rewrite in
`next.config.ts` proxies `/api/v1/*` to the backend. This works for both
single-host dev and remote dev (where `localhost:8000` from the browser
points at the wrong machine).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.dev.yaml

@@ -0,0 +1,7 @@
+services:
+  api:
+    volumes:
+      - ./api/services/telephony/providers/three_cx:/app/api/services/telephony/providers/three_cx:ro
+      - ./api/services/telephony/providers/__init__.py:/app/api/services/telephony/providers/__init__.py:ro
+      - ./api/schemas/telephony_config.py:/app/api/schemas/telephony_config.py:ro
+      - ./api/alembic/versions:/app/api/alembic/versions:ro

ui/.env.example

@@ -1,3 +1,3 @@
 BACKEND_URL=http://localhost:8000
-NEXT_PUBLIC_BACKEND_URL=http://localhost:8000
+NEXT_PUBLIC_BACKEND_URL=
 NEXT_PUBLIC_NODE_ENV=development

ui/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "ui",
-  "version": "1.30.1",
+  "version": "1.31.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "ui",
-      "version": "1.30.1",
+      "version": "1.31.0",
       "dependencies": {
         "@dagrejs/dagre": "^1.1.4",
         "@radix-ui/react-alert-dialog": "^1.1.15",