feat: PHP 8.4 compatibility and owncloud.online design

[BWTECH-github]

Summary

This PR brings full PHP 8.4 compatibility to ownCloud Core along with a custom design theme for owncloud.online.

Changes

PHP 8.4 Compatibility

• Updated composer.json to require PHP >= 8.4
• Fixed deprecated implicit nullable type declarations across the codebase
• Fixed str_replace() type errors (e.g. LDAP port as string)
• Fixed explode() and other string functions receiving null instead of string
• Updated return types and parameter types for PHP 8.4 strict typing
• Resolved Deprecated: Creation of dynamic property warnings
• Fixed ArrayAccess offset type compatibility
• Updated CI/CD workflows for PHP 8.4

owncloud.online Design

• Custom login page design with owncloud.online branding
• Updated color scheme and styling
• Design preview included: core/img/design-preview.png

LDAP Test Fix

• getLdapPort():int → getLdapPortAsString():string
• Fixes str_replace() type error in LDAP acceptance tests (related to [tests-only] test: return the LDAP port number as a string #41500)

Testing

• All PHP 8.4 deprecation warnings resolved
• Composer dependency check passes with PHP >= 8.4

Stats

• 300+ files changed
• 3 commits

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Maintained by BW.Tech

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