fix(install): guard multisite table access during sqlite install

[MiddleSokilAI]

Summary

• Guard sMultisite runtime listeners until the s_multisites table exists.
• Keep OnLoadSettings in default-site mode during CLI installation before package migrations finish.
• Skip manager/tree/SSO listeners that query multisite rows until migrations have created the table.

Root Cause

During SQLite CLI installs the package plugin can be loaded before its migration has created s_multisites. The OnLoadSettings listener then queries the model immediately, and SQLite fails on the missing table.

Validation

• php8.4 -l plugins/sMultisitePlugin.php
• php8.4 -l database/migrations/2023_08_31_150405_create_s_multisites_table.php
• php8.4 -l database/migrations/2025_12_17_000000_add_site_color_to_multisites.php
• composer validate --no-check-publish --no-check-all
• git diff --check

Full evo install ... --db-type=sqlite reproduction was not run in this local checkout.

Closes #2