Add bulk import feature for players

[torfinnnome]

• Add bulk import form to import multiple players from CSV, TSV, or TXT files
• Support file upload and direct paste of player data
• Auto-detect separator (tab, comma, or semicolon)
• Allow mixed 2-column and 3-column formats in same import

Fixes #85.

Thanks for making Coronate! I was missing this feature, when organising an event at our local school.

[netlify]

👷 Deploy request for coronate accepted.

Name	Link
🔨 Latest commit	f753cad
🔍 Latest deploy log	https://app.netlify.com/projects/coronate/deploys/691218328cf9db00082d9751

[johnridesabike]

Thanks for the contribution. I haven't had a chance to review it in detail, but this seems like a useful addition. Normally I'd ask that we add a test for the CSV parser, but the test suite is unfortunately broken right now so that may have to wait until we fix/replace that too.

Once I have a chance for a closer review, I we can merge this if there aren't any issues.