feat(#370): install mosaicstack-telemetry in Coordinator

- Add mosaicstack-telemetry>=0.1.0 to pyproject.toml dependencies
- Configure Gitea PyPI registry via pip.conf (extra-index-url)
- Integrate TelemetryClient in FastAPI lifespan (start_async/stop_async)
- Store client on app.state.mosaic_telemetry for downstream access
- Create mosaic_telemetry.py helper module with:
  - get_telemetry_client(): retrieve client from app state
  - build_task_event(): construct TaskCompletionEvent with coordinator defaults
  - create_telemetry_config(): create config from MOSAIC_TELEMETRY_* env vars
- Add 28 unit tests covering config, helpers, disabled mode, and lifespan
- New module has 100% test coverage

Refs #370

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

apps/coordinator/src/main.py

@@ -9,6 +9,7 @@ from pathlib import Path
 from typing import Any
 
 from fastapi import FastAPI
+from mosaicstack_telemetry import TelemetryClient  # type: ignore[import-untyped]
 from pydantic import BaseModel
 from slowapi import Limiter, _rate_limit_exceeded_handler
 from slowapi.errors import RateLimitExceeded
@@ -18,6 +19,7 @@ from starlette.responses import Response
 
 from .config import settings
 from .coordinator import Coordinator
+from .mosaic_telemetry import create_telemetry_config
 from .queue import QueueManager
 from .telemetry import TelemetryService, shutdown_telemetry
 from .webhook import router as webhook_router
@@ -76,6 +78,18 @@ async def lifespan(app: FastAPI) -> AsyncIterator[dict[str, Any]]:
         telemetry_service.initialize()
         logger.info("OpenTelemetry telemetry initialized")
 
+    # Initialize Mosaic telemetry client
+    mosaic_telemetry_config = create_telemetry_config()
+    mosaic_telemetry_client: TelemetryClient | None = None
+    if mosaic_telemetry_config.enabled:
+        mosaic_telemetry_client = TelemetryClient(mosaic_telemetry_config)
+        await mosaic_telemetry_client.start_async()
+        app.state.mosaic_telemetry = mosaic_telemetry_client
+        logger.info("Mosaic telemetry client started")
+    else:
+        app.state.mosaic_telemetry = None
+        logger.info("Mosaic telemetry disabled via configuration")
+
     # Initialize queue manager
     queue_file = Path("queue.json")
     queue_manager = QueueManager(queue_file=queue_file)
@@ -115,6 +129,11 @@ async def lifespan(app: FastAPI) -> AsyncIterator[dict[str, Any]]:
                 pass
         logger.info("Coordinator stopped")
 
+    # Shutdown Mosaic telemetry client
+    if mosaic_telemetry_client is not None:
+        await mosaic_telemetry_client.stop_async()
+        logger.info("Mosaic telemetry client stopped")
+
     # Shutdown OpenTelemetry
     if telemetry_enabled:
         shutdown_telemetry()