Add blueprint validation to CI

[thetic]

Summary

• Add validation scripts for Home Assistant blueprints in .github/scripts/
• Validates YAML syntax with HA-specific tags (!input, !include, !secret, !env_var)
• Checks schema compliance (required name/domain fields, valid domain values)
• Detects duplicate blueprint names across the repository
• Adds new blueprint job to CI workflow

Test plan

• Verify CI workflow runs successfully
• Test validation catches invalid YAML syntax
• Test validation catches missing required fields

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.68%. Comparing base (002dddb) to head (675d9a0).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main       #5   +/-   ##
=======================================
  Coverage   98.68%   98.68%           
=======================================
  Files           6        6           
  Lines         304      304           
=======================================
  Hits          300      300           
  Misses          4        4           

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