BUG: Restore UTC fallback without timezonefinder

[ting-hong-shieh]

Pull request type

• Code changes (bugfix)
• Code maintenance (tests)

Checklist

• A regression test covers the missing optional dependency
• Docs were reviewed; no update is needed because the intended UTC fallback is unchanged
• Ruff formatting and lint checks pass
• Pylint reports 10.00/10 for the changed files
• CHANGELOG.md — no action needed; an LLM workflow auto-updates it after merge

Current behavior

When EnvironmentAnalysis receives no explicit timezone, it uses the optional
timezonefinder dependency to select one from the launch coordinates. If that
dependency is unavailable, the fallback handler calls warnings.warning, which
does not exist. Construction stops with AttributeError before UTC can be
selected.

New behavior

The fallback now calls warnings.warn, emits the existing message, selects UTC,
and localizes naive input dates. The regression test exercises the public
constructor while forcing the optional import to fail.

Breaking change

• No

Verification

• pytest tests/unit/environment/test_environment_analysis.py::test_missing_timezonefinder_defaults_to_utc -q — 1 passed
• pytest tests/unit/environment -m "not slow" -q — 159 passed, 6 deselected
• ruff check rocketpy/environment/environment_analysis.py tests/unit/environment/test_environment_analysis.py
• ruff format --check rocketpy/environment/environment_analysis.py tests/unit/environment/test_environment_analysis.py
• pylint rocketpy/environment/environment_analysis.py tests/unit/environment/test_environment_analysis.py — 10.00/10

[Gui-FernandesBR]

If it passes on CI, we can merge it!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.16%. Comparing base (e0ff281) to head (78f55a5).
⚠️ Report is 49 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1143      +/-   ##
===========================================
+ Coverage    82.18%   83.16%   +0.97%     
===========================================
  Files          122      129       +7     
  Lines        16355    16901     +546     
===========================================
+ Hits         13441    14055     +614     
+ Misses        2914     2846      -68     

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