fix(florence2): load legacy large-ft checkpoints on transformers>=5.14 (#2123)

The published Florence-2 large-ft checkpoints label their BART text config with
the legacy remote-code model_type "florence2_language" and route the processor
through torch remote code, so they fail to load on the native Florence-2 support
in transformers>=5.14 (KeyError: florence2_language, or a torch ImportError).
Register the legacy config as a BART config, force the native torch-free
processor path, and fall back to CLIPImageProcessor when torchvision is absent.
Also mark the encoder-decoder model no_chunked_prefill so the decoder-only
chunked prefill (which trims the prompt but not the encoder mask) does not run.