fix(#7892): restore "now" (marcus bains) line to planning views

[shefalijoshi]

Closes #7892

Describe your changes:

Initialize alignment offset to 0. (it was undefined). This fixes the now line issue.
Also handle a small bug with swimlane configuration not getting replaced when the plan used by a gantt chart was changed

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Author Checklist

• Changes address original issue?
• Tests included and/or updated with changes?
• Has this been smoke tested?
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• Testing instructions included in associated issue OR is this a dependency/testcase change?

Reviewer Checklist

• Changes appear to address issue?
• Reviewer has tested changes by following the provided instructions?
• Changes appear not to be breaking changes?
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• Code style and in-line documentation are appropriate?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 57.40%. Comparing base (7f8b5e0) to head (628fe36).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7898      +/-   ##
==========================================
+ Coverage   57.11%   57.40%   +0.29%     
==========================================
  Files         676      676              
  Lines       27355    27357       +2     
  Branches     2685     2685              
==========================================
+ Hits        15623    15705      +82     
+ Misses      11394    11314      -80     
  Partials      338      338              

Flag	Coverage Δ
e2e-ci	62.38% <ø> (-0.07%)	⬇️
e2e-full	41.77% <ø> (+18.31%)	⬆️
unit	49.29% <100.00%> (+0.01%)	⬆️

Files with missing lines	Coverage Δ
src/plugins/plan/components/PlanView.vue	59.49% <100.00%> (+0.17%)	⬆️
src/ui/components/TimeSystemAxis.vue	65.88% <100.00%> (-3.17%)	⬇️

... and 9 files with indirect coverage changes

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[ozyx]

LGTM