fix(database): add UPTIME_KUMA_SQLITE_SINGLE_CONNECTION

[louislam]

Summary

• Resolves SQLITE_BUSY: database is locked errors #7289

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[Copilot]

Pull request overview

Adds an opt-in environment variable to force SQLite to use a single Knex pool connection, intended to mitigate SQLITE_BUSY: database is locked issues reported on some Raspberry Pi/SD-card setups.

Changes:

• Introduces UPTIME_KUMA_SQLITE_SINGLE_CONNECTION to switch SQLite pool config from { min: 0, max: 20 } to { min: 1, max: 1 }.
• Refactors SQLite pool configuration to use a shared poolConfig object and spread it into the Knex pool config.

[CommanderStorm]

not a fan.. grumpf

[louislam]

Indeed, but I think it is the only solution for Pi users for now. I wish we could find an universal solution with this env var.

[CommanderStorm]

I don't think that supporting EMMC is reasonable tbh