Engineering firm seeks library software

I am looking for library software for a North German engineering firm. In order to consolidate our book collections, I am looking for suitable library software to digitally catalog them in their entirety. The collection currently comprises approximately 10,000 books, which I would like to catalog. The main focus is on architecture/construction. In addition, there are also German-language dictionaries and encyclopedias, atlases/maps, and other items - approximately 1,000 photographs. Some of the books are older, which raises the question of how I can quickly catalog them. ISBNs can only be used for newer books. Is there any way to access the catalogs of larger libraries?

The software should meet the following requirements:

• User management
• Recording of holdings
• Cataloging
• Search function
• Searching the holdings
• ISBN management
• Data entry, barcodes
• Loans (only to a very limited extent)
• Recording of library subgroups (departments) – e.g., regional history, geography, construction literature, etc.
• Ideally, also management of photographs
• Support for mobile devices (iOS)
• Web-based – but not a must

Two software workstations are planned. MS Windows systems will be used.