Improve affine decomposition

[LucaMarconato]

Claude generated PR description, manually verified

Port the RQ-based decomposition algorithm from Spatial-Innovation-Team/transfo
to replace the old 2D-only, theta-based rotation logic in
_decompose_transformation. The new algorithm is dimension-generic, warns on
ill-conditioned linear parts, and encodes the reflection as a single
axis flip instead of an arbitrary diagonal matrix.

Drop the spatialdata-specific restrictions that no longer apply: the z axis
and the c channel are now decomposed like any other axis, and axes are
allowed to come out in a different order between input and output (checked
by axis set rather than exact tuple order).

Split _decompose_transformation into _decompose_transformation_simple and
_decompose_transformation_full, each returning a fixed-size tuple of the
component transformations instead of a Sequence, so callers get a
concretely-typed tuple (2 vs. 5 components) rather than a Union.

Reorganize the tests into TestSimpleDecomposition/TestFullDecomposition
classes, consolidating round-trip coverage into a single
DECOMPOSE_TRANSFORMATION_CASES table (with descriptive ids) shared by both
classes, and keeping only the checks that can't be expressed as a
matrix-in/reconstructed-matrix-out case (warnings, component types/arity,
algorithmic invariants).

[codecov]

Codecov Report

❌ Patch coverage is 97.72727% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.40%. Comparing base (11039c7) to head (2f10ecd).

Files with missing lines	Patch %	Lines
src/spatialdata/transformations/transformations.py	97.72%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1186      +/-   ##
==========================================
- Coverage   92.41%   92.40%   -0.02%     
==========================================
  Files          52       52              
  Lines        7874     7869       -5     
==========================================
- Hits         7277     7271       -6     
- Misses        597      598       +1     

Files with missing lines	Coverage Δ
src/spatialdata/transformations/transformations.py	90.82% <97.72%> (-0.26%)	⬇️

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[LucaMarconato]

@Tomaz-Vieira can you please review?

Also, the GitHub diff view is not the most useful for this PR since the code is now split into functions. I suggest to use a standard diff view, so that most of the code is easily shown as untouched.