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 98.14815% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.39%. Comparing base (8731a46) to head (eb66dd5).

Files with missing lines	Patch %	Lines
src/spatialdata/transformations/transformations.py	98.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1186      +/-   ##
==========================================
- Coverage   92.41%   92.39%   -0.02%     
==========================================
  Files          52       52              
  Lines        7875     7868       -7     
==========================================
- Hits         7278     7270       -8     
- Misses        597      598       +1     

Files with missing lines	Coverage Δ
src/spatialdata/transformations/transformations.py	90.79% <98.14%> (-0.29%)	⬇️

🚀 New features to boost your workflow:

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

[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.

[Tomaz-Vieira]

The decomposition is a very nice maneuver =)

My comments are more on the code organization side of things; in particular, I argue for expressing the requirements of the functions more clearly, and leaving most of the responsibility of meeting those requirements to the callers of the functions.

[LucaMarconato]

@Tomaz-Vieira thanks for the review, really helpful! I have addressed all the review comments. I have also renamed the two functions form decompose_affine_simple/full to:

• _decompose_into_linear_and_translation
• _decompose_into_5_simple_transformations (not sure if it's a good name).

I will merge as it is required for the bounding box PR; if we need to change something (like the name of the functions) we can do it in a follow up PR; they are private and unreleased anyway.

[LucaMarconato]

Had to do a manual rebase as I stacked PRs complained about the merge commit.