feat(#374): add telemetry config to docker-compose and .env

- Add MOSAIC_TELEMETRY_* variables to .env.example with descriptions
- Pass telemetry env vars to api service in production compose
- Pass telemetry env vars to coordinator service in dev and swarm composes
- Swarm composes default to production URL (https://tel-api.mosaicstack.dev)
- Dev compose includes commented-out telemetry-api service placeholder
- All compose files default MOSAIC_TELEMETRY_ENABLED to false for safety

Refs #374

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

.env.example

@@ -350,6 +350,32 @@ OLLAMA_MODEL=llama3.1:latest
 # Get your API key from: https://platform.openai.com/api-keys
 # OPENAI_API_KEY=sk-...
 
+# ======================
+# Mosaic Telemetry (Task Completion Tracking & Predictions)
+# ======================
+# Telemetry tracks task completion patterns to provide time estimates and predictions.
+# Data is sent to the Mosaic Telemetry API (a separate service).
+
+# Master switch: set to false to completely disable telemetry (no HTTP calls will be made)
+MOSAIC_TELEMETRY_ENABLED=true
+
+# URL of the telemetry API server
+# For Docker Compose (internal): http://telemetry-api:8000
+# For production/swarm: https://tel-api.mosaicstack.dev
+MOSAIC_TELEMETRY_SERVER_URL=http://telemetry-api:8000
+
+# API key for authenticating with the telemetry server
+# Generate with: openssl rand -hex 32
+MOSAIC_TELEMETRY_API_KEY=your-64-char-hex-api-key-here
+
+# Unique identifier for this Mosaic Stack instance
+# Generate with: uuidgen or python -c "import uuid; print(uuid.uuid4())"
+MOSAIC_TELEMETRY_INSTANCE_ID=your-instance-uuid-here
+
+# Dry run mode: set to true to log telemetry events to console instead of sending HTTP requests
+# Useful for development and debugging telemetry payloads
+MOSAIC_TELEMETRY_DRY_RUN=false
+
 # ======================
 # Logging & Debugging
 # ======================