feat: add --disable-otel / DISABLE_OTEL to disable otel trace export

[galexrt]

Add flag/env var to allow disabling OTEL export/traces.

This should eliminate logs such as this when there isn't OTEL export available at localhost:4318:

[09:59:59.043] INFO: traces export: Post "https://localhost:4318/v1/traces": dial tcp [::1]:4318: connect: connection refused
[09:34:34.057] INFO: traces export: Post "https://localhost:4318/v1/traces": dial tcp [::1]:4318: connect: connection refused
[09:49:49.062] INFO: traces export: Post "https://localhost:4318/v1/traces": dial tcp [::1]:4318: connect: connection refused

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Are there any steps I'm missing to build the project? I can't seem to build it due to "docs" pkg missing:

internal/http/publicapi/public_api.go:11:2: no required module provides package github.com/fivemanage/lite/docs; to add it:
        go get github.com/fivemanage/lite/docs

Looking around, the web/package.json target generate:api accesses the docs/ dir as well, but there is no docs/ dir after following the steps from the README.md.
I would appreciate any hints to get it to build locally so I can test it and also look into fixing another issue (nil panics when clickhouse is disabled/not used).

[Copilot]

Pull request overview

This PR adds a --disable-otel CLI flag and DISABLE_OTEL environment variable to allow users to opt out of OpenTelemetry trace export. This is intended to eliminate noisy connection-refused log messages when no OTEL collector is running at localhost:4318.

Changes:

• pkg/otel/exporter.go: Adds a disabled bool parameter to SetupTracer and InstallExportPipeline; when disabled is true, sets up a bare (no-exporter) tracer provider instead of connecting to the OTLP endpoint.
• cmd/lite/lite.go: Registers the --disable-otel flag and binds it to the DISABLE_OTEL env var via viper; passes the value into otel.SetupTracer.
• README.md / .env.template: Documents the new DISABLE_OTEL configuration option.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
pkg/otel/exporter.go	Core logic change: skips OTLP exporter setup when disabled=true
cmd/lite/lite.go	Registers --disable-otel flag and wires it to viper/env
README.md	Adds DISABLE_OTEL to the configuration table
.env.template	Adds DISABLE_OTEL=false to the dev template

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[Copilot]

The --disable-otel CLI flag is registered with rootCmd.Flags().Bool(...) but there is no viper.BindPFlag("disable-otel", rootCmd.Flags().Lookup("disable-otel")) call, unlike other flags such as port and dsn. Without this binding, viper.GetBool("disable-otel") will never read the value supplied via the command-line flag — it will only pick up the value from the DISABLE_OTEL environment variable. To make the flag functional, a corresponding viper.BindPFlag call must be added alongside the existing viper.BindEnv call.

[Copilot]

When OTEL is disabled, the code creates a full SDK trace.NewTracerProvider() with no exporter but with the default sampler (ParentBased(AlwaysSample)). This means spans are still allocated in memory throughout the application — they are just never exported. A more efficient approach would be to use otel.NewNoopTracerProvider() (from go.opentelemetry.io/otel) instead, which provides a true no-op implementation that skips span creation entirely and incurs zero overhead.

Suggested change

	tracerProvider := trace.NewTracerProvider()
	tracerProvider := otel.NewNoopTracerProvider()