Fix new test warnings (issue #971)

[ilayfalach]

Summary

Fixes the hera-owned deprecation warnings reported in #971 (introduced/surfaced after #882):

• hera/utils/logging/helpers.py: replaced deprecated importlib.resources.read_text with files().joinpath().read_text().
• Eliminated invalid escape sequences across hera/ sources (LaTeX docstrings made raw, OpenFOAM banner strings backslash-escaped) and added a repo-wide regression test (test_no_invalid_escapes.py) so new instances are caught automatically. Pre-existing dead files with unrelated SyntaxErrors are skipped by the test rather than silently ignored.
• hera/riskassessment/agents/effects/InjuryLevel.py: plt.close('all') before each plt.switch_backend() call to avoid matplotlib's "Auto-close()ing of figures upon backend switching" deprecation.
• hera/measurements/GIS/raster/topography.py: fixed pyproj's "ndim > 0 to a scalar" DeprecationWarning — reproduced against the exact pinned CI versions (geopandas 1.0.1 / pyproj 3.6.1 / numpy 1.26.4) in an isolated venv; GeoDataFrame.to_crs() on a 1-row frame triggers it, so single-point conversions now go through a scalar pyproj Transformer instead.
• matplotlibCountour.py's ContourSet.collections warning was already fixed on master (verified, no change needed).
• CI: added JUPYTER_PLATFORM_DIRS=1 to silence jupyter_client's platformdirs migration notice.

Warnings originating in the vendored hermes/pyargos repos (cloned into _vendor/ by CI) are tracked separately and require PRs to those repos.

Test plan

• hera/tests/test_logging_helpers.py (new) — asserts no DeprecationWarning loading the default logging config
• hera/tests/test_no_invalid_escapes.py (new) — compiles every hera/**/*.py file with escape warnings as errors
• hera/tests/test_topography.py (extended) — new regression tests for the single-point CRS conversion warning
• hera/tests/test_riskassessment_flow.py — passes with -W error::matplotlib.MatplotlibDeprecationWarning
• Full suite (pytest hera/tests/ -m "not slow" --ignore=hera/tests/test_notebooks.py): 645 passed, 10 skipped, 1 xfailed, no unexpected warnings
• Confirm CI's warnings summary no longer lists the hera-owned items from Fix new warnings from test #971

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