Rewrite BlazeGraph connection guide with practical instructions

[kmcginnes]

Description

The BlazeGraph connection guide was only 2 vague bullet points with no actionable information. Rewrote it to match the quality of the Gremlin Server guide:

• Docker command to run BlazeGraph
• Exact connection form values for Graph Explorer
• Note about custom namespaces
• Docker networking section with step-by-step instructions for container-to-container communication

Validation

Verified the BlazeGraph Docker image name and default SPARQL endpoint path are correct.

Related Issues

• Part of Update content to be more clear and focused #1159

Check List

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I have verified pnpm checks passes with no errors.
• I have verified pnpm test passes with no failures.
• I have covered new added functionality with unit tests if necessary.
• I have updated documentation if necessary.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.67%. Comparing base (c5affc5) to head (6b7b71a).
⚠️ Report is 143 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1699       +/-   ##
===========================================
+ Coverage   47.81%   72.67%   +24.86%     
===========================================
  Files         382      408       +26     
  Lines        8525    12286     +3761     
  Branches     3159     3525      +366     
===========================================
+ Hits         4076     8929     +4853     
+ Misses       3070     2339      -731     
+ Partials     1379     1018      -361     

Flag	Coverage Δ
unittests	72.67% <ø> (+24.86%)	⬆️

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