Draft: Synchronize master branch with 2025-patches

Includes:

• Reference update for 2025-patches based on lhcb-2025-patches/159 (!5389 (merged))
• Add a workaround for Allen standalone not having GAUDI_VERSION.h available (!5391 (merged))
• Support old-style Generator FSRs in mergeDST [2025-patches] (!5384 (merged))
• Prepare LHCb v57r15 (!5410 (merged))
• Remove tilda backup files from Det/DetCond/tests/refs (!5419 (merged))
• Prepare LHCb v57r16 (!5425 (merged))