feat: add opentelemetry middleware to web server

[DCchoudhury15]

What this PR does / why we need it:
This PR integrates OpenTelemetry (OTEL) middleware into the Gin web server to enable tracing and observability, as requested in #23.

Which issue(s) this PR fixes:
Fixes #23

Special notes for your reviewer:

• New Middleware: Added otelgin middleware to the Gin router in pkg/servers/web/server.go.
• Refactoring: Refactored NewServer to accept a Service interface instead of the concrete e2b implementation. This was necessary to resolve a circular dependency between the web and e2b packages.
• Dependencies: Updated go.mod to include go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin.

[kruise-bot]

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[codecov]

Codecov Report

❌ Patch coverage is 78.94737% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.07%. Comparing base (deda1a7) to head (a3d3c60).
⚠️ Report is 63 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/servers/web/server.go	76.47%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #79      +/-   ##
==========================================
+ Coverage   50.95%   51.07%   +0.12%     
==========================================
  Files          87       88       +1     
  Lines        4814     4826      +12     
==========================================
+ Hits         2453     2465      +12     
- Misses       2149     2151       +2     
+ Partials      212      210       -2     

Flag	Coverage Δ
unittests	51.07% <78.94%> (+0.12%)	⬆️

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[DCchoudhury15]

cc @furykerry pr up for review

[DCchoudhury15]

@AiRanthem up for review

[furykerry]

@DCchoudhury15 the patch seems incomplete, no one will call NewServer

[DCchoudhury15]

@furykerry implemented the fix up for review

[kruise-bot]

@DCchoudhury15: PR needs rebase.

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