Add OTLP/Jaeger tracing support for daemon and coordinator

[Nakshatra480]

Closes #1313

Summary

Implements OTLP tracing for dora-daemon and dora-coordinator, enabling distributed tracing via Jaeger when the DORA_OTLP_ENDPOINT environment variable is set.

Changes

• telemetry.rs: Added service name to OTLP Resource for proper service identification in Jaeger
• lib.rs: Registered global tracer provider to enable span export
• daemon.rs: Runtime-safe OTLP initialization with OtelGuard lifetime management
• coordinator.rs: Runtime-safe OTLP initialization with OtelGuard lifetime management

Key Technical Details

The implementation addresses a critical async/sync challenge: OTLP uses async gRPC (Tonic) but daemon/coordinator initialize tracing before creating the tokio runtime. The solution uses conditional two-phase initialization:

1. Check for OTLP environment variables (sync)
2. Create tokio runtime
3. Initialize OTLP tracing inside runtime context (async)
   Additionally, the OtelGuard must be stored for the lifetime of the runtime to prevent the tracer provider from shutting down immediately after initialization.

Testing

Tested with Jaeger all-in-one:

# Start Jaeger
docker run -d --name jaeger \
  -p 4317:4317 \
  -p 16686:16686 \
  jaegertracing/all-in-one:latest

# Run dora with tracing
export DORA_OTLP_ENDPOINT="http://localhost:4317"
./target/release/dora up
./target/release/dora start examples/rust-dataflow/dataflow.yml

# View traces at http://localhost:16686

[Nakshatra480]

@haixuanTao @phil-opp changes are ready, pls review it