Bug/fix inappropriate symbol and ! for factorial

[m-messer]

Requires #247 to be merged first before merging this PR.

Problem

Two bugs affecting infinity and factorial handling in symbolic expression comparison:

1. The Unicode infinity symbol (∞) was not recognised as valid input, causing parse errors when students used it.
2. Comparing infinite expressions (e.g. oo = oo) would subtract the two sides before checking, but oo - oo evaluates to nan in SymPy rather than 0, causing incorrect results. A KeyError/TypeError could also be thrown during the is_infinite check.
3. The triple factorial notation !!! was silently mishandled — it parses as repeated ! (factorial of factorial of factorial) rather than the mathematical triple factorial, with no warning to the student.

Fix

• Added ∞ as an alias for oo in expression_utilities.py so the Unicode symbol is accepted as input.
• Added do_comparison_infinite in context/symbolic.py that compares infinite expressions directly (e.g. lhs == rhs) instead of via subtraction, and wrapped the is_infinite check in a try/except to guard against edge-case exceptions.
• Added a NOTATION_WARNING_TRIPLE_FACTORIAL feedback message and wired it up in evaluation.py to warn students that !!! is not supported.

Other changes

• Upgraded to Python 3.12, SymPy 1.14, and mpmath 1.4.1; updated CI workflows accordingly.
• Fixed the Dockerfile: switched base image package manager, added find to installed requirements, set PYTHONPATH, and updated the CMD entrypoint format.

[m-messer]

Database testing can be found here: https://github.com/lambda-feedback/compareExpressions/actions/runs/25786405204/job/75740792212

7 errors out of 1000

1. _Grade Mismatch - eval func True, DB False -- Answer 2(cos(pi/2)+isin(pi/2)), response 2( cos(π/2)+i sin(π/2))

• Added support for unicode greek letters in a previous fix

2. E^{x log x} ( log x + 1) could not be parsed as a valid mathematical expression. Ensure that correct codes for input symbols are used, correct notation is used, that the expression is unambiguous and that all parentheses are closed.
   • Answer written in LaTeX not Sympy
3. 2x \ sin x + x^{2} \ cos x could not be parsed as a valid mathematical expression. Ensure that correct codes for input symbols are used, correct notation is used, that the expression is unambiguous and that all parentheses are closed.

• Same as 2.

4. x E^{x}(2+x) could not be parsed as a valid mathematical expression. Ensure that correct codes for input symbols are used, correct notation is used, that the expression is unambiguous and that all parentheses are closed.

• Same as 2.

5. asec**2(ax) could not be parsed as a valid mathematical expression. Ensure that correct codes for input symbols are used, correct notation is used, that the expression is unambiguous and that all parentheses are closed.

• Invalid form for asec^2(ax), should be asec(ax)**2

6. _Grade Mismatch - eval func True, DB False -- Answer -5 muA, response -5 µA

• Added support for unicode greek letters in a previous fix

7. (x cosx - sinx) / (x^{2}) could not be parsed as a valid mathematical expression. Ensure that correct codes for input symbols are used, correct notation is used, that the expression is unambiguous and that all parentheses are closed.

• Same as 2.