fix: Jaeger image tag and remap PG/Valkey ports to avoid host conflicts

jaegertracing/jaeger:2 is not a valid Docker Hub tag — pin to 2.6.0.
Remap PG to 5433 and Valkey to 6380 to avoid conflicts with existing
host containers (sage-postgres, mosaic-valkey on 5432/6379).
Ports are env-configurable via PG_HOST_PORT / VALKEY_HOST_PORT.

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

.env.example

@@ -1,8 +1,12 @@
-# Database
-DATABASE_URL=postgresql://mosaic:mosaic@localhost:5432/mosaic
+# Database (port 5433 avoids conflict with host PostgreSQL)
+DATABASE_URL=postgresql://mosaic:mosaic@localhost:5433/mosaic
 
-# Valkey (Redis-compatible)
-VALKEY_URL=redis://localhost:6379
+# Valkey (Redis-compatible, port 6380 avoids conflict with host Redis/Valkey)
+VALKEY_URL=redis://localhost:6380
+
+# Docker Compose host port overrides (optional)
+# PG_HOST_PORT=5433
+# VALKEY_HOST_PORT=6380
 
 # OpenTelemetry
 OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318