[Draw/walk area task] Prevent user from drawing self-intersecting polygons

[anandwana001]

Fixes #3234

This PR introduces a full system to detect and handle polygon self-intersections:

Implemented isSelfIntersecting(vertices) to check for crossing edges, with support for both open polylines and closed polygons.

Integrated validation into the workflow:
Add Point: checks the newly added edge, reverts the vertex, and shows a dialog if self-intersection is detected.
Complete Polygon: validates the would-be closed ring (vertices + first), blocking completion and showing a dialog if invalid.
Ensured the intersection flag resets when geometry is valid, preventing stale “intersecting” states.
Updated onFeatureUpdated to disable the Complete button when a polygon is invalid.

Added unit tests covering:
Open and closed polygons
Adjacent edges sharing vertices
True self-intersections (e.g., “X” shapes)
Edge cases like empty list, single point, or triangles

This provides reliable guardrails to prevent creating invalid polygons and ensures user feedback when intersections occur.

Screen.Recording.2025-08-21.at.9.16.31.AM.mov

@gino-m @jo-spek PTAL?

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.17%. Comparing base (a435ed8) to head (2d652ba).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...acollection/tasks/polygon/DrawAreaTaskViewModel.kt	46.66%	4 Missing and 4 partials ⚠️
...tacollection/tasks/polygon/DrawAreaTaskFragment.kt	62.50%	0 Missing and 3 partials ⚠️
.../org/groundplatform/android/ui/util/PolygonUtil.kt	96.87%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #3235   +/-   ##
=========================================
  Coverage     67.16%   67.17%           
- Complexity     1411     1415    +4     
=========================================
  Files           303      303           
  Lines          7642     7664   +22     
  Branches        774      785   +11     
=========================================
+ Hits           5133     5148   +15     
  Misses         2076     2076           
- Partials        433      440    +7     

Files with missing lines	Coverage Δ
.../groundplatform/android/model/geometry/Geometry.kt	69.81% <100.00%> (ø)
.../org/groundplatform/android/ui/util/PolygonUtil.kt	89.58% <96.87%> (-0.42%)	⬇️
...tacollection/tasks/polygon/DrawAreaTaskFragment.kt	73.86% <62.50%> (-2.04%)	⬇️
...acollection/tasks/polygon/DrawAreaTaskViewModel.kt	81.11% <46.66%> (-0.98%)	⬇️

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[gino-m]

@anandwana001

[gino-m]

@anandwana001 Note I updated the PR description to reflect the new behavior rather than a description of the code