Fix multiple bugs: TypeScript strict mode errors, PHP division by zero, null dereference, and logic issues

[itriedcoding]

Summary

This PR fixes multiple bugs found through static analysis and code review across both the TypeScript frontend and PHP backend.

TypeScript Fixes (12 errors)

• Added explicit event handler type annotations to fix all
  oImplicitAny errors in strict mode across: Checkbox, Modal, Switch, JavaVersionModalFeature, FileEditContainer, UploadButton, AllocationRow, VariableBox

PHP Fixes

High Severity:

• NodeRepository: Fixed division by zero when $maxUsage is 0 (e.g., memory/disk with no overallocation and base value of 0)
• NodeRepository: Changed join() to leftJoin() in getUsageStats and getUsageStatsRaw to prevent null dereference when a node has no servers
• StartupModificationService: Fixed pass-by-reference variable reassignment bug where $server = ->forceFill(...) created a new local variable instead of updating the caller's $server, causing egg_id/nest_id changes to be lost

Medium Severity:

• BuildModificationService: Initialized $freshlyAllocated = null before the conditional block to prevent undefined variable when �dd_allocations is empty but
  emove_allocations is not
• ProcessScheduleService: Fixed $job->failed() being called twice when exception is not a DaemonConnectionException
• AssignmentService: Added try/catch around transaction body to properly roll back on exception, preventing connection pool exhaustion

Low Severity:

• Node model: Removed duplicate 'description' entry in $fillable array