fix: reconcile pydantic v2 config names and drop unused fields

[ToxicBiohazard]

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply.

• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).
• Documentation Update (if none of the other choices applies).

Proposed changes

Reconcile the config leftovers from the Pydantic v2 migration.

Fixes #189
Fixes #190

• Remove settings that nothing reads: APRIL_ROLE_1, APRIL_ROLE_2, RANK_FIVE, RANK_TWENTY_FIVE, RANK_FIFTY, RANK_HUNDRED, ACADEMY_CBBH, APRIL_FLAG_1, APRIL_FLAG_2, SLACK_WEBHOOK, and JIRA_SPOILER_WEBHOOK. extra="forbid" will reject them if they are still set.
• Seed dynamic roles from ROLE__{suffix} instead of the pre-migration ROLE_ prefix.
• Choose the settings file with APP_ENV_FILE. BOT_ENVIRONMENT still works, so current Vault configs keep booting. Either flag loads ENV_PATH when it is set.
• Build the database URL in one place. ASYNC selects asyncmy or pymysql, and Alembic calls that builder with the sync driver instead of reading MYSQL_*.

Checklist

Put an x in the boxes that apply.

• I have read and followed the CONTRIBUTING.md doc.
• Lint and unit tests pass locally with my changes.
• I have added the necessary documentation (if appropriate).

Additional context

startup.sh still uses MYSQL_* for the readiness ping. .docker.env already defines both MYSQL_* and DATABASE__*.

Before deploy, Vault still needs:

• SEASON_ID set to the real season. .test.env already has it. A local .env may still only have CURRENT_SEASON_ID.
• The removed keys deleted, or startup fails. That includes JIRA_SPOILER_WEBHOOK if it is still present.

Made with Cursor

[codecov]

Codecov Report

❌ Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.05%. Comparing base (76b2f25) to head (243f57a).

Files with missing lines	Patch %	Lines
scripts/seed_dynamic_roles.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #195      +/-   ##
==========================================
- Coverage   66.60%   66.05%   -0.55%     
==========================================
  Files          54       55       +1     
  Lines        3177     3226      +49     
==========================================
+ Hits         2116     2131      +15     
- Misses       1061     1095      +34     

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