Fix bugs for rotor with supports

[jguarato]

Resolves #1189

---

This pull request addresses three main issues related to the rotor model with supports:

1. Allow multiple bearing elements on the same shaft node:
Previously, it was not possible to attach more than two bearing elements to the same shaft node. Adjustments have been made to enable this behavior.

2. Fix error in run_ucs when using supports:
An error was occurring in the run_ucs function when the model included supports in the bearings. Specific corrections were implemented to handle this case. ⚠️ This fix still needs further verification.

3. Fix error in run_freq_response when speed is zero:
In a specific case involving supports, the solver was returning eigenvalues equal to zero. Because the speed being analyzed was also zero, this caused the transfer_matrix to contain NaN values. A fix was applied to handle this scenario and prevent such behavior.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 60.78431% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.60%. Comparing base (07a5a63) to head (df7bfc3).
⚠️ Report is 167 commits behind head on main.

Files with missing lines	Patch %	Lines
ross/rotor_assembly.py	61.22%	19 Missing ⚠️
ross/point_mass.py	50.00%	1 Missing ⚠️
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1195      +/-   ##
==========================================
- Coverage   82.91%   75.60%   -7.31%     
==========================================
  Files          39       38       -1     
  Lines        8247     8494     +247     
==========================================
- Hits         6838     6422     -416     
- Misses       1409     2072     +663     

Files with missing lines	Coverage Δ
ross/point_mass.py	85.71% <50.00%> (+0.23%)	⬆️
ross/rotor_assembly.py	92.70% <61.22%> (-1.17%)	⬇️

... and 2 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bb99529...df7bfc3. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[jguarato]

Fixed problem related to bearing plotting with scale factor different from unit

Previous:

Now: