Fix KSP enum codegen with Convert annotation

[jbl428]

resovles #1410

Problem

Enum fields with @Convert annotation were generating SimplePath instead of EnumPath, preventing enum-specific operations like coalesce().

Solution

Added early enum type check in TypeExtractor.userType() to ensure enums are processed by referenceType() before checking user type annotations.

Changes

• Modified TypeExtractor.kt to skip enum types in userType()
• Added isEnum() helper function
• Added test case verifying coalesce() works on enum with @Convert

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (bef31eb) to head (9c4f072).
⚠️ Report is 28 commits behind head on master.

Files with missing lines	Patch %	Lines
...n/kotlin/com/querydsl/ksp/codegen/TypeExtractor.kt	0.00%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #1411    +/-   ##
=======================================
  Coverage    0.00%   0.00%            
=======================================
  Files         813     838    +25     
  Lines       31271   31605   +334     
  Branches     3550    3559     +9     
=======================================
- Misses      31271   31605   +334     

Flag	Coverage Δ
cubrid	0.00% <0.00%> (?)
db2	0.00% <0.00%> (?)
embedded	0.00% <0.00%> (?)
examples	0.00% <ø> (?)
firebird	0.00% <0.00%> (?)
mongodb	0.00% <0.00%> (?)
mysql	0.00% <0.00%> (?)
oracle	0.00% <0.00%> (?)
postgresql	0.00% <0.00%> (?)
test	0.00% <0.00%> (ø)

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