Fix DECT relay container: install node_modules at /workspace, not under agent

The runtime container failed with ERR_MODULE_NOT_FOUND: axios when
integrations/cisco-dect/client.js tried to load. Root cause is
Node's ESM resolver: it walks UP from the IMPORTING file looking
for node_modules, never sideways into siblings.

Container filesystem before:
  /workspace/dect-relay-agent/node_modules/       <- axios lives here
  /workspace/dect-relay-agent/index.js            <- ok, finds it by walking up
  /workspace/integrations/cisco-dect/client.js    <- walks up to /, never sees axios

Node 20.20 has --experimental-detect-module ON by default, so
client.js is still treated as ESM (starts with `import`), and the
resolver correctly reports "cannot find package 'axios'" rather
than syntax-erroring on the import keyword. But it still can't find
the package — the location is wrong.

Fix: install node_modules at /workspace/ so BOTH the agent AND the
shared modules can find it by walking up.

  /workspace/node_modules/                        <- axios here now
  /workspace/package.json                         <- also here, "type":"module" for all descendants
  /workspace/dect-relay-agent/index.js            <- walks up to /workspace/node_modules ✓
  /workspace/integrations/cisco-dect/client.js    <- walks up to /workspace/node_modules ✓
  /workspace/utils/httpDigestAuth.js              <- same ✓

WORKDIR moves from /workspace/dect-relay-agent to /workspace, and
CMD changes accordingly:
  node --enable-source-maps dect-relay-agent/index.js

Rebuild + reship the bundle with `./dect-relay-agent/bundle.sh` and
`./install.sh` on the DC host — it's an idempotent upgrade.

Verified locally (agent modules import cleanly using the same
directory shape as the container).

dect-relay-agent/Dockerfile

@@ -28,6 +28,22 @@
 # it as a tarball, and ships the tarball. The DC only runs
 # `docker load` + `docker compose up -d` — zero network calls beyond
 # the initial docker load.
+#
+# WHERE node_modules LIVES (subtle but critical):
+#   /workspace/node_modules   ← NOT under dect-relay-agent/
+#
+# The agent imports `../integrations/cisco-dect/client.js`, which
+# in turn does `import axios from 'axios'`. Node's ESM resolver
+# walks UP from the IMPORTING file (client.js) looking for
+# node_modules — it does NOT search siblings. So if node_modules
+# lived at /workspace/dect-relay-agent/node_modules, then
+# client.js (at /workspace/integrations/cisco-dect/client.js) would
+# never find axios and blow up with ERR_MODULE_NOT_FOUND at runtime.
+# Placing node_modules one level higher fixes it: both the agent
+# AND the shared integrations resolve axios via /workspace/node_modules.
+# The package.json at /workspace/ also declares "type":"module" so
+# every .js file under /workspace/ is treated as ESM without needing
+# its own package.json.
 
 # ─── Stage 1: builder ────────────────────────────────────────────────
 # Installs prod deps in a full node image (has python/build-essentials
@@ -37,10 +53,12 @@
 
 FROM node:20-alpine AS builder
 
-WORKDIR /workspace/dect-relay-agent
+WORKDIR /workspace
 
 # Copy just the package manifest first so this layer caches across
-# code-only changes.
+# code-only changes. The agent's package.json IS the workspace
+# package.json — same "type":"module", same deps (ws / axios /
+# dotenv), just placed one directory higher.
 COPY dect-relay-agent/package.json ./package.json
 
 # Install only production deps. --ignore-scripts because we don't run
@@ -60,21 +78,26 @@ FROM node:20-alpine AS runtime
 # baseline hardening we get essentially for free.
 USER node
 
-# Match the repo layout so relative imports (`../integrations/...`)
-# resolve exactly as they do in development.
-WORKDIR /workspace/dect-relay-agent
+# WORKDIR is the workspace root so `node dect-relay-agent/index.js`
+# resolves correctly AND node_modules at /workspace/node_modules is
+# discoverable by both the agent and the shared modules.
+WORKDIR /workspace
 
-# Ship the node_modules we built in stage 1. Ownership goes to `node`
-# so the process can read them without needing root.
-COPY --from=builder --chown=node:node /workspace/dect-relay-agent/node_modules ./node_modules
+# Shared node_modules (see the header comment for why it's here and
+# not under dect-relay-agent/). Ownership goes to `node` so the
+# process can read them without needing root.
+COPY --from=builder --chown=node:node /workspace/node_modules ./node_modules
 
-# Agent source + manifest.
+# Package manifest at workspace root — Node uses this to determine
+# "type":"module" for every .js file under /workspace/**.
 COPY --chown=node:node dect-relay-agent/package.json ./package.json
-COPY --chown=node:node dect-relay-agent/index.js ./index.js
+
+# Agent source.
+COPY --chown=node:node dect-relay-agent/index.js ./dect-relay-agent/index.js
 
 # Shared modules the agent imports from the parent workspace.
-COPY --chown=node:node integrations/cisco-dect /workspace/integrations/cisco-dect
-COPY --chown=node:node utils/httpDigestAuth.js /workspace/utils/httpDigestAuth.js
+COPY --chown=node:node integrations/cisco-dect ./integrations/cisco-dect
+COPY --chown=node:node utils/httpDigestAuth.js ./utils/httpDigestAuth.js
 
 # Optional metadata that shows up in `docker inspect` output — useful
 # in the DC for "which build am I running?" without needing to poke
@@ -92,4 +115,4 @@ LABEL org.opencontainers.image.title="dect-relay-agent" \
 # Node handles SIGTERM natively when the process installs handlers
 # (which we do in index.js). --enable-source-maps improves stack
 # traces if something crashes at runtime — cheap and always-on.
-CMD ["node", "--enable-source-maps", "index.js"]
+CMD ["node", "--enable-source-maps", "dect-relay-agent/index.js"]