REFACTOR: implement proper exceptions

Refactoring Task

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Problem description

All error handling is currently done using generic Errors.

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Affected Components/Files:

• src/app/_components/create-exhibtion-modal.tsx
• src/components/exhibition-editor.tsx
• src/hooks/exhibition-actions.ts
• • other files where errors are thrown

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Tasks:

• Create custom descriptive exceptions for possible errors.
• Throw replace generic errors with custom ones where appropriate
• Identify errors based on type not the error message.

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Acceptance Criteria:

• CUstom exceptions are used where necessary
• Errors are identified based on type, not error message