Allow clip_filter for energy-based trend analyses

[martin-springer]

Summary
This PR enables the clip_filter to be used in energy-based analyses by falling back to pv_energy when pv_power is not available. It also adds validation to ensure the data has sufficient time resolution for clipping detection.

Changes
analysis_chains.py

• Modified TrendAnalysis._filter() to use pv_energy for clip filtering when pv_power is None
• Added frequency validation that raises a ValueError if the median time step exceeds 60 minutes, as clipping detection requires sub-hourly data
• Simplified the clip_filter logic by introducing a clip_data variable that selects the appropriate data source
  analysis_chains_test.py
• Added test_clip_filter_frequency_error() to verify that the frequency validation raises an appropriate error for low-resolution data (e.g., 2-hour intervals)
  docs/sphinx/source/changelog/pending.rst
• Added changelog entries under "Enhancements" section

Motivation

When users provide energy data directly (via pv_input="energy"), the pv_power attribute is None. Previously, this would cause the trend analysis to fail and raise a ValueError. This change allows clipping detection to work with energy data, provided the time resolution is adequate (≤60 minutes).

• Code changes are covered by tests
• Code changes have been evaluated for compatibility/integration with TrendAnalysis
• [ ] New functions added to __init__.py
• [ ] API.rst is up to date, along with other sphinx docs pages
• Example notebooks are rerun and differences in results scrutinized
• Updated changelog

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.22%. Comparing base (b5fc7c4) to head (7462f46).

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #474      +/-   ##
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- Coverage        96.26%   96.22%   -0.04%     
===============================================
  Files               12       12              
  Lines             2276     2279       +3     
===============================================
+ Hits              2191     2193       +2     
- Misses              85       86       +1     

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