Resolve OTel serviceVersion at runtime instead of persisting it

[ChrisJBurns]

Summary

• Moves serviceVersion resolution from config creation time to runtime in NewProvider(), so it always reflects the running binary version
• Stops persisting the version in DefaultConfig(), MaybeMakeConfig(), createTelemetryConfig(), and operator's NormalizeTelemetryConfig()
• Existing configs with an explicit serviceVersion (e.g., from the K8s operator CRD) are still honored
• Previously, restarting a workload after upgrading ToolHive would report the old version in traces/metrics; thv export would also capture the stale version

Closes #2296

Test plan

• go test ./pkg/telemetry/... passes
• go test ./cmd/thv-operator/pkg/spectoconfig/... passes
• go test ./cmd/thv-operator/pkg/vmcpconfig/... passes
• Lint passes
• Manual: start server with otel, check version in traces, upgrade binary, restart, verify version updates

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.77%. Comparing base (c8f2254) to head (db12600).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/telemetry/config.go	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3789      +/-   ##
==========================================
- Coverage   66.78%   66.77%   -0.01%     
==========================================
  Files         437      437              
  Lines       43002    43005       +3     
==========================================
  Hits        28718    28718              
- Misses      12078    12081       +3     
  Partials     2206     2206              

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