feat: foundation — Docker Compose, OTEL, shared types (P0-002, P0-005, P0-006)

Docker Compose (P0-005):
- PG 17 + pgvector, Valkey 8, OTEL Collector, Jaeger
- OTEL Collector config with trace/metric/log pipelines
- .env.example with all connection strings

OTEL Foundation (P0-006):
- @opentelemetry/sdk-node with auto-instrumentations
- tracing.ts loaded before NestJS bootstrap
- OTLP HTTP exporter → collector → Jaeger
- Disabled fs/dns instrumentations (noisy)

Shared Types (P0-002):
- ChatMessageDto with class-validator (IsUUID, IsNotEmpty, MaxLength)
- ChatResponseDto for REST responses
- Socket.IO typed event maps (ServerToClientEvents, ClientToServerEvents)
- AgentSessionHandle opaque type
- All event payload interfaces shared across gateway/cli/discord

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infra/otel-collector.yml

@@ -0,0 +1,35 @@
+receivers:
+  otlp:
+    protocols:
+      grpc:
+        endpoint: 0.0.0.0:4317
+      http:
+        endpoint: 0.0.0.0:4318
+
+processors:
+  batch:
+    timeout: 1s
+    send_batch_size: 1024
+
+exporters:
+  otlp/jaeger:
+    endpoint: jaeger:4317
+    tls:
+      insecure: true
+  debug:
+    verbosity: basic
+
+service:
+  pipelines:
+    traces:
+      receivers: [otlp]
+      processors: [batch]
+      exporters: [otlp/jaeger, debug]
+    metrics:
+      receivers: [otlp]
+      processors: [batch]
+      exporters: [debug]
+    logs:
+      receivers: [otlp]
+      processors: [batch]
+      exporters: [debug]