fix: convert stored link_filters list to search_link mapping form

[Shindhu-Ramaswamy]

Fixes #2692

Fix

parseLinkFilters() now converts the stored list into the dict form before it is
used — same as Desk's parse_filters() in form/controls/link.js. eval: values
are evaluated against { doc, parent } like Desk does.

Updated the call sites in Field.vue, SidePanelLayout.vue and Grid.vue to pass
the doc context. Added unit tests.

To reproduce

1. Add a custom Link field → User on CRM Lead with
   Link Filters = [["User","user_type","=","System User"]].
2. Add it to the Lead side panel and click it.
3. Before: empty dropdown, search_link returns 500.
   After: only System Users are listed.

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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge with no new findings.

_{Reviews (3) · Last reviewed commit: "fix: evaluate eval: link_filters against..."}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.86%. Comparing base (e4bd5d9) to head (dd2b59f).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2865      +/-   ##
===========================================
+ Coverage    71.51%   71.86%   +0.35%     
===========================================
  Files          180      181       +1     
  Lines        12757    12859     +102     
===========================================
+ Hits          9123     9241     +118     
+ Misses        3634     3618      -16     

Files with missing lines	Coverage Δ
frontend/src/utils/fieldTransforms.js	100.00% <100.00%> (ø)

... and 5 files with indirect coverage changes

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