fix: prefill template fields with meta default on new ticket page

[RitvikSardana]

Template fields on the new ticket page were always initialized empty, ignoring the field's default set in meta (DocField / Custom Field / Property Setter).

• get_one API now returns default for each template field
• New ticket page prefills the field value with it

Test: set a default on an HD Ticket field via Customize Form, add it to the ticket template, open the new ticket page. The field comes prefilled.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 74.30%. Comparing base (c037dcf) to head (f5ed4d0).
⚠️ Report is 249 commits behind head on develop.

Files with missing lines	Patch %	Lines
...elpdesk/helpdesk/doctype/hd_ticket_template/api.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3675      +/-   ##
===========================================
+ Coverage    71.63%   74.30%   +2.66%     
===========================================
  Files          145      149       +4     
  Lines        10106    11082     +976     
===========================================
+ Hits          7239     8234     +995     
+ Misses        2867     2848      -19     

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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

_{Reviews (2): Last reviewed commit: "fix: normalize Check field defaults on t..." | Re-trigger Greptile}