feat: enforce otel-only tracing in service and lambda scaffolding [DEV-590]

[negarciacamilo]

Description

Removes the X-Ray tracing fallback from lambda and service scaffolding so every generated lambda and service is wired for OpenTelemetry only, including new lambdas added to existing legacy X-Ray services — this forces migration instead of letting new code perpetuate X-Ray. Also fixes stale/hardcoded otel-layer ARNs and a missing serverless.yml block, aligns the generated OTel spans and logging with the monorepo's observability.md conventions, removes a chunk of dead domain-scaffolding code found along the way, and drops a broken/unused plugin while adding one that was missing.

Task Context

What is the current behavior?

• new:lambda detected whether the target service was already on OTel or X-Ray and generated the matching tracing code, meaning a legacy X-Ray service kept getting new X-Ray-instrumented lambdas indefinitely.
• The worker layer (resources.go, worker.go, idempotency.go) always used the legacy X-Ray tracer regardless of the service's tracing mode — this branch was never actually wired to OTel.
• serverless.yml.tmpl hardcoded the OTel collector and Datadog extension layer ARNs directly instead of referencing the shared config/sls/layers.yml, and those hardcoded ARNs were already stale. It also lacked the custom.group metadata block and serverless-plugin-lambda-deployments, both present in nearly every real service.
• Draft embedded and generated its own copy of collector.yaml and duplicated OTel-managed env vars in environment.yml, both of which can drift from the monorepo's SSoT.
• Generated lambda code added spans to DI/Provide functions and private idempotency helpers, and worker spans in HTTP lambdas discarded their context — all against the monorepo's observability.md conventions. The SQS/SNS+SQS idempotency template also referenced an undeclared base package, so generated code didn't compile (only caught by manual review — the test suite only checks template syntax, not full compilation).
• Idempotency error/panic paths used the legacy logger.Get() instead of log.Get(), breaking log↔trace correlation; the same legacy logger was used in domain provider files.
• One domain service span used a snake_case operation name instead of the required kebab-case.
• Draft's new:domain computed and unit-tested a whole providers/ package (generator, service, postgres/repository) that was never actually written to disk — pure dead code.
• new:service offered a "warmup" plugin option that 0 of 41 real services use, and package.json.tmpl always installed serverless-plugin-datadog, which observability.md says is legacy-X-Ray-only and should not be present for OTel services.

What is the new behavior?

• All lambda and service scaffolding (handler bootstrap and worker layers, across all lambda types) generates OTel instrumentation only — the X-Ray branch and the UseOtel detection/flag have been removed entirely.
• serverless.yml.tmpl now references the shared config/sls/layers.yml for ARNs, adds the custom.group/deploymentSettings blocks and serverless-plugin-lambda-deployments, matching real services; new:service runs mage otel:fix post-create so the collector config and environment section stay synced with the monorepo's source of truth.
• Removed spans from DI/Provide functions and idempotency helpers (handler/worker spans remain, since those are real entry points); HTTP worker spans now propagate their context onto the echo request so downstream calls nest correctly; fixed the missing base package import so SQS/SNS+SQS lambdas actually compile.
• Replaced logger.Get() with log.Get() (trace-correlated *Context variants) everywhere the legacy logger was used, in both lambda and domain templates; fixed the log package import path and a stray broken variable reference along the way; fixed a snake_case span operation name to kebab-case.
• Deleted the dead providers/ package templates and their loaders/tests — verified against a real domain (betsettlements) that the actually-generated service/provide.go + repository/provide.go already match the standardized DI pattern used across the monorepo.
• Removed the warmup plugin end-to-end (flag, prompt, template, package.json) and removed serverless-plugin-datadog from package.json.tmpl.
• go.mod/go.sum dependencies bumped (aws-sdk-go-v2, sentry-go, testify, x/crypto, huh, and related transitive deps) to go 1.25, with the pre-commit hook's pinned go.mod version updated to match.

Additional Context

Two other legacy X-Ray branches exist (feat/otel-support, feat/otel-scaffolding-support) that appear superseded by work already merged into this branch.