Document (or extend) which dask.array APIs respect array.backend for host literals

When using the CuPy array backend (`dask.config.set({"array.backend": "cupy"})` or
equivalent), **factory-style** constructors such as `dask.array.zeros` produce
collections with CuPy chunk meta, but **host literals** passed through
`dask.array.atleast_1d` or `dask.array.from_array(numpy_buffer)` still yield
**NumPy-meta** Dask arrays.

I would like this behaviour to be **explicitly documented** in Dask array
backend docs. Optionally, I'm interested in whether scalar promotion could
ever respect the active `array.backend` when the input is a Python scalar (not
only when the user passes a CuPy buffer explicitly).

### Minimal reproducer
```python
import dask
import dask.array as da
import numpy as np
with dask.config.set({"array.backend": "cupy"}):
import cupy as cp # noqa: F401 — register backend
z = da.zeros((2, 2))
literal = da.atleast_1d(1.5e9)
from_np = da.from_array(np.array([1.0, 2.0], dtype=np.float32), chunks=(2,))
z_meta = type(z._meta).__module__
lit_meta = type(literal._meta).__module__
from_meta = type(from_np._meta).__module__
print("zeros meta:", z_meta) # cupy — follows array.backend
print("atleast_1d(float) meta:", lit_meta) # numpy — does not
print("from_array(np) meta:", from_meta) # numpy — follows input buffer
```

On a CuPy-enabled environment we observe:
```
zeros → cupy
atleast_1d(1.5e9) → numpy
from_array(np.ndarray(...)) → numpy
```

### Questions for maintainers
- Is this intended? If so, which operations are guaranteed to honour `array.backend` vs which always follow the dtype/module of the host buffer?

- Should `da.atleast_1d(scalar)` under array.backend=cupy ever produce CuPy-meta chunks, or should callers always use `da.from_array(cupy.asarray([...]))`?

- If the design is “input array type wins for from_array”, could the docs state that clearly next to the array.backend configuration guide?

Environment
```
dask==2024.10.0 (also please note if behaviour differs across versions)
Python 3.11+
cupy + CUDA (CuPy wheel matching local toolkit)
```
### What would help downstream

A short table in the array backend documentation: operation → respects array.backend / respects input buffer / notes.
If behaviour changes in a future release, mention it in release notes so libraries can drop workarounds.