fix(sqlalchemy): support values-based sa.Enum columns

[aiolibsbot]

What

Fix a crash when an admin model uses a values-based sa.Enum column
(e.g. sa.Enum("active", "inactive")).

Why

Values-based enums have no member class, so sa.Enum.python_type is
str. The SelectInput choice builder iterated python_type directly,
raising TypeError: 'type' object is not iterable and crashing
SAResource construction for a first-class, documented SQLAlchemy
pattern. Only class-based enums (sa.Enum(MyEnumClass)) worked before.

How

Branch on sa.Enum.enum_class:

• class-based (enum_class set): iterate the member class — id = member
  value, name = member name (unchanged, matches the JSON encoder which
  emits enum.value).
• values-based (enum_class is None): use the enums string list, with
  each string as both id and name.

Testing

• New test_values_based_enum (reproduces the crash pre-fix) and
  test_class_based_enum (regression guard for existing behavior).
• Full suite: 99 passed, 1 xfailed. The lone test_admin_view failure is
  pre-existing and unrelated (Broken tests #934).

Advances #666 (TODO cleanup).

---

Quality Report

Changes: 2 files changed, 42 insertions(+), 2 deletions(-)

Code scan: clean

Tests: failed (command not found)

Branch hygiene: clean

Generated by Kōan

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.66%. Comparing base (2448fd1) to head (b950470).
⚠️ Report is 168 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1169      +/-   ##
==========================================
+ Coverage   95.56%   95.66%   +0.09%     
==========================================
  Files          21       21              
  Lines        2954     2976      +22     
  Branches      193      201       +8     
==========================================
+ Hits         2823     2847      +24     
+ Misses        105      103       -2     
  Partials       26       26              

Flag	Coverage Δ
integration	80.84% <33.33%> (-0.12%)	⬇️
js	83.89% <ø> (ø)
unit	97.60% <100.00%> (+0.18%)	⬆️

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