Wireup metrics for sing-box

[AGMETEOR]

• Add versioning to builds
• Add metrics similar/compatible to those of http-proxy

[Copilot]

Pull request overview

This PR adds versioning support to sing-box builds and integrates OpenTelemetry metrics compatible with http-proxy. The changes include a new OTEL metrics package, updates to existing metrics to use renamed metric names and add directional attributes, version information passed via build flags, and proxy configuration reading from INI files.

• Version information is now injected at build time via ldflags
• New OTEL package provides telemetry endpoint configuration and meter provider initialization
• Metrics updated to use proxy.io and proxy.connections naming compatible with http-proxy
• Geo-location tracking added via country code lookup from client IPs

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
otel/otel.go	New package for OTEL metrics initialization with customizable endpoint and resource attributes
metrics/metrics.go	Refactored to use renamed metrics (proxy.io, proxy.connections) and added geo-location lookup
metrics/conn.go	Updated to use new metric names and add direction attributes for read/write operations
metrics/packet_conn.go	Updated to use new metric names and add direction attributes for packet read/write
cmd/main.go	Added version variables, ProxyInfo struct, and OTEL initialization in pre-run hook
cmd/cmd_run.go	Added proxy info file reading function and version logging
go.mod	Updated Go version and added new dependencies for OTEL, geo-lookup, and INI parsing
go.sum	Checksum updates for new and updated dependencies
Dockerfile	Modified to accept build arguments for version injection
.github/workflows/push.yaml	Added build-args to inject version info during Docker builds

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[garmr-ulfr]

Other than the two comments, looks good.