通过 env 调节调度周期

[felinae98]

This change is 

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[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.

Project coverage is 85.27%. Comparing base (9f16633) to head (4921621).
Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
nonebot_bison/scheduler/scheduler.py	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #684      +/-   ##
==========================================
+ Coverage   85.00%   85.27%   +0.27%     
==========================================
  Files          97       98       +1     
  Lines        5520     5670     +150     
==========================================
+ Hits         4692     4835     +143     
- Misses        828      835       +7     

Flag	Coverage Δ
smoke-test	85.27% <85.71%> (+0.27%)	⬆️

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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):