通过 env 调节调度周期

[felinae98]

This change is 

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[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 84.97%. Comparing base (9f16633) to head (4921621).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
nonebot_bison/scheduler/scheduler.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #684      +/-   ##
==========================================
- Coverage   85.00%   84.97%   -0.03%     
==========================================
  Files          97       97              
  Lines        5520     5532      +12     
==========================================
+ Hits         4692     4701       +9     
- Misses        828      831       +3     

Flag	Coverage Δ
smoke-test	84.97% <81.81%> (-0.03%)	⬇️

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[Copilot]

Pull Request Overview

This PR introduces the ability to adjust scheduling intervals via environment variables.

• Loads the site-specific scheduling rule from configuration in scheduler.py
• Adds a new ScheduleConfig model and bison_site_schedule configuration in plugin_config.py
• Updates the documentation to illustrate how to configure scheduling via environment variables

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
nonebot_bison/scheduler/scheduler.py	Added a new helper method to load schedule rules from plugin_config and updated the scheduler initialization
nonebot_bison/plugin_config.py	Introduced ScheduleConfig and bison_site_schedule as configurable options
docs/usage/README.md	Added usage instructions and examples for the BISON_SITE_SCHEDULE environment variable

[Copilot]

The method name '_load_scehdule_rule_from_config' contains a spelling error. Consider renaming it to '_load_schedule_rule_from_config' for clarity.

Suggested change

	def _load_scehdule_rule_from_config(self):
	def _load_schedule_rule_from_config(self):