feat(live): task 1.5.1 — WS server scaffold + heartbeat

Stand up the WebSocket live-broadcast server inside the Processor process:
- src/live/server.ts: createLiveServer factory with start/stop lifecycle,
  per-connection LiveConnection type, sendOutbound helper with back-pressure
  guard, 30s frame-level heartbeat via ws ping/pong, pluggable onMessage
  handler (stub returns error/not-implemented until 1.5.2/1.5.3).
- src/live/protocol.ts: zod schemas for inbound subscribe/unsubscribe messages,
  all outbound types (subscribed/unsubscribed/position/error), WsCloseCodes.
- src/shared/types.ts: extracted Metrics interface so src/live/ can import it
  without crossing the enforced src/live/ ↔ src/core/ ESLint boundary.
- src/core/types.ts: re-exports Metrics from shared/types to keep Phase 1
  call sites unchanged.
- src/config/load.ts: LIVE_WS_PORT, LIVE_WS_HOST, LIVE_WS_PING_INTERVAL_MS,
  LIVE_WS_DRAIN_TIMEOUT_MS, LIVE_WS_BACKPRESSURE_THRESHOLD_BYTES,
  DIRECTUS_BASE_URL, DIRECTUS_AUTH_TIMEOUT_MS, DIRECTUS_AUTHZ_TIMEOUT_MS,
  LIVE_BROADCAST_GROUP_PREFIX, LIVE_BROADCAST_BATCH_SIZE,
  LIVE_BROADCAST_BATCH_BLOCK_MS, LIVE_DEVICE_EVENT_REFRESH_MS.
- src/observability/metrics.ts: Phase 1.5 metrics inventory (connections,
  inbound/outbound counters, auth/authz histograms, subscription gauge,
  broadcast counters + lag histogram, snapshot histograms, device-event map).
- src/main.ts: wires the live server alongside the durable-write consumer;
  shutdown order: live server → consumer → metrics → Redis → Postgres.
- eslint.config.js: import/no-restricted-paths zones for src/live/ ↔ src/core/.
- test/live-server.test.ts: 7 unit tests covering connect, ping, protocol
  violation, valid message dispatch, connections gauge, and stop() drain.

pnpm-lock.yaml

@@ -20,6 +20,9 @@ importers:
       prom-client:
         specifier: ^15.1.3
         version: 15.1.3
+      ws:
+        specifier: ^8.20.0
+        version: 8.20.0
       zod:
         specifier: ^3.23.8
         version: 3.25.76
@@ -30,6 +33,9 @@ importers:
       '@types/pg':
         specifier: ^8.11.10
         version: 8.20.0
+      '@types/ws':
+        specifier: ^8.18.1
+        version: 8.18.1
       '@typescript-eslint/eslint-plugin':
         specifier: ^8.19.0
         version: 8.59.1(@typescript-eslint/parser@8.59.1(eslint@9.39.4)(typescript@5.9.3))(eslint@9.39.4)(typescript@5.9.3)
@@ -722,6 +728,9 @@ packages:
   '@types/ssh2@1.15.5':
     resolution: {integrity: sha512-N1ASjp/nXH3ovBHddRJpli4ozpk6UdDYIX4RJWFa9L1YKnzdhTlVmiGHm4DZnj/jLbqZpes4aeR30EFGQtvhQQ==}
 
+  '@types/ws@8.18.1':
+    resolution: {integrity: sha512-ThVF6DCVhA8kUGy+aazFQ4kXQ7E1Ty7A3ypFOe0IcJV8O/M511G99AW24irKrW56Wt44yG9+ij8FaqoBGkuBXg==}
+
   '@typescript-eslint/eslint-plugin@8.59.1':
     resolution: {integrity: sha512-BOziFIfE+6osHO9FoJG4zjoHUcvI7fTNBSpdAwrNH0/TLvzjsk2oo8XSSOT2HhqUyhZPfHv4UOffoJ9oEEQ7Ag==}
     engines: {node: ^18.18.0 || ^20.9.0 || >=21.1.0}
@@ -2567,6 +2576,18 @@ packages:
   wrappy@1.0.2:
     resolution: {integrity: sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ==}
 
+  ws@8.20.0:
+    resolution: {integrity: sha512-sAt8BhgNbzCtgGbt2OxmpuryO63ZoDk/sqaB/znQm94T4fCEsy/yV+7CdC1kJhOU9lboAEU7R3kquuycDoibVA==}
+    engines: {node: '>=10.0.0'}
+    peerDependencies:
+      bufferutil: ^4.0.1
+      utf-8-validate: '>=5.0.2'
+    peerDependenciesMeta:
+      bufferutil:
+        optional: true
+      utf-8-validate:
+        optional: true
+
   xtend@4.0.2:
     resolution: {integrity: sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==}
     engines: {node: '>=0.4'}
@@ -3065,6 +3086,10 @@ snapshots:
     dependencies:
       '@types/node': 18.19.130
 
+  '@types/ws@8.18.1':
+    dependencies:
+      '@types/node': 22.19.17
+
   '@typescript-eslint/eslint-plugin@8.59.1(@typescript-eslint/parser@8.59.1(eslint@9.39.4)(typescript@5.9.3))(eslint@9.39.4)(typescript@5.9.3)':
     dependencies:
       '@eslint-community/regexpp': 4.12.2
@@ -5269,6 +5294,8 @@ snapshots:
 
   wrappy@1.0.2: {}
 
+  ws@8.20.0: {}
+
   xtend@4.0.2: {}
 
   y18n@5.0.8: {}