text: Title: FastAPI integration error
  Body: ### Description
  
  I apologize if this belongs in the FastAPI issues instead of logfire. I'm not really sure who is the culprit here. 
  
  I'm attaching a [sample project](https://github.com/user-attachments/files/16090524/example.zip) to demonstrate an error when `logfire[fastapi]` is added to a FastAPI project.
  
  > **Note:** forcing a downgrade to pydantic v1 fixes the issue _(or removing logfire all together)_
  
  
  ### Error Reproduction
  
  A simple API without any input works:
  
  ```shell
  curl "http://localhost:8000/hello/"
  ```
  
  Calling an API with a pydantic model as input fails:
  
  ```shell
  curl -X POST "http://localhost:8000/test/" -H "Content-Type: application/json" -d '{"name": "test"}'
  ````
  
  Error log:
  ```
  INFO:     127.0.0.1:58776 - "POST /test/ HTTP/1.1" 500 Internal Server Error
  ERROR:    Exception in ASGI application
  Traceback (most recent call last):
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/uvicorn/protocols/http/httptools_impl.py", line 399, in run_asgi
      result = await app(  # type: ignore[func-returns-value]
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/uvicorn/middleware/proxy_headers.py", line 70, in __call__
      return await self.app(scope, receive, send)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/fastapi/applications.py", line 1054, in __call__
      await super().__call__(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/applications.py", line 123, in __call__
      await self.middleware_stack(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/middleware/errors.py", line 186, in __call__
      raise exc
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/middleware/errors.py", line 164, in __call__
      await self.app(scope, receive, _send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 631, in __call__
      await self.app(scope, otel_receive, otel_send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/middleware/exceptions.py", line 65, in __call__
      await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/_exception_handler.py", line 64, in wrapped_app
      raise exc
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
      await app(scope, receive, sender)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/routing.py", line 756, in __call__
      await self.middleware_stack(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/routing.py", line 776, in app
      await route.handle(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/routing.py", line 297, in handle
      await self.app(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/routing.py", line 77, in app
      await wrap_app_handling_exceptions(app, request)(scope, receive, send)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/_exception_handler.py", line 64, in wrapped_app
      raise exc
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
      await app(scope, receive, sender)
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/starlette/routing.py", line 72, in app
      response = await func(request)
                 ^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/fastapi/routing.py", line 269, in app
      solved_result = await solve_dependencies(
                      ^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/logfire/_internal/integrations/fastapi.py", line 111, in patched_solve_dependencies
      return await instrumentation.solve_dependencies(request, original)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/logfire/_internal/integrations/fastapi.py", line 173, in solve_dependencies
      result = await original
               ^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/fastapi/dependencies/utils.py", line 628, in solve_dependencies
      ) = await request_body_to_args(  # body_params checked above
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/fastapi/dependencies/utils.py", line 758, in request_body_to_args
      v_, errors_ = field.validate(value, values, loc=loc)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/fastapi/_compat.py", line 127, in validate
      self._type_adapter.validate_python(value, from_attributes=True),
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/pydantic/type_adapter.py", line 142, in wrapped
      return func(self, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/pydantic/type_adapter.py", line 373, in validate_python
      return self.validator.validate_python(object, strict=strict, from_attributes=from_attributes, context=context)
             ^^^^^^^^^^^^^^
    File "/Users/mcantrell/.pyenv/versions/3.11.9/lib/python3.11/functools.py", line 1001, in __get__
      val = self.func(instance)
            ^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/pydantic/type_adapter.py", line 142, in wrapped
      return func(self, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/acme/fastapi-pydantic-error/.venv/lib/python3.11/site-packages/pydantic/type_adapter.py", line 318, in validator
      assert isinstance(self._validator, SchemaValidator)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  AssertionError
  ```
  
  To fix the problem, either remove logfire completely or downgrade pydantic to v1.
  
  ### Python, Logfire & OS Versions, related packages (not required)
  
  ```TOML
  requests="2.32.3"
  pydantic="2.8.0"
  fastapi="0.111.0"
  protobuf="4.25.3"
  rich="13.7.1"
  executing="2.0.1"
  opentelemetry-api="1.25.0"
  opentelemetry-exporter-otlp-proto-common="1.25.0"
  opentelemetry-exporter-otlp-proto-http="1.25.0"
  opentelemetry-instrumentation="0.46b0"
  opentelemetry-instrumentation-asgi="0.46b0"
  opentelemetry-instrumentation-fastapi="0.46b0"
  opentelemetry-proto="1.25.0"
  opentelemetry-sdk="1.25.0"
  opentelemetry-semantic-conventions="0.46b0"
  opentelemetry-util-http="0.46b0"
  ```
  