[!] add OpenTelemetry tracing and metrics support

[pashagolub]

• Add OTelOpts config struct
• Add internal/otel package: Provider, Tracer, Meter, Shutdown, Noop
• Add 5 metric instruments
• Instrument executeChain and executeTask with spans and metrics
• Wire real provider in main.go with graceful shutdown
• ValidateOTel() validates endpoint scheme, ratio, and timeouts
• Protocol auto-detected from URL scheme (grpc:// vs http(s)://)
• Headers are YAML-only (prevents secrets in shell history)
• Fallback to Noop provider on init failure

[coveralls]

Coverage Report for CI Build 27361355738

Coverage decreased (-0.6%) to 89.778%

Details

• Coverage decreased (-0.6%) from the base build.
• Patch coverage: 33 uncovered changes across 5 files (236 of 269 lines covered, 87.73%).
• 9 coverage regressions across 2 files.

Uncovered Changes

File	Changed	Covered	%
internal/otel/otel.go	139	127	91.37%
internal/otel/metrics.go	59	49	83.05%
main.go	13	8	61.54%
internal/config/config.go	23	19	82.61%
internal/scheduler/chain.go	33	31	93.94%
Total (6 files)	269	236	87.73%

Coverage Regressions

9 previously-covered lines in 2 files lost coverage.

File	Lines Losing Coverage	Coverage
internal/pgengine/log_hook.go	6	81.08%
internal/scheduler/chain.go	3	86.06%

---

Coverage Stats

Relevant Lines:	2250
Covered Lines:	2020
Line Coverage:	89.78%
Coverage Strength:	1.02 hits per line

---

💛 - Coveralls

[0xgouda]

I am testing this and noticed that there are no INFO log messages for metrics/traces collection or upload, which in my opinion is nice to have to be able to confirm that things are working as expected and maybe help in deubgging in some scenarios.

[0xgouda]

Thinking Out Loud: How can one configure 2 different endpoints, one for trace exportation and one for metrics?

[pashagolub]

no INFO log messages for metrics/traces collection or upload

What? In what way log messages are connected to metrics and traces? What am I missing here?