Logs: array attribute values are silently dropped (and diverge from sentry-javascript)

### Environment

`sentry-sdk` 2.61.0, Python 3.14, logs enabled via `enable_logs=True`.

### What happened

Passing a list-valued attribute to `sentry_sdk.logger.*` results in the attribute **silently disappearing** from the Logs UI — no value, no warning, no debug log.

```python
sentry_sdk.logger.info(
"workflow_engine processed event",
attributes={
"workflow_ids": [101, 202, 303], # list[int] -> dropped (blank in UI)
"rule_names": ["high_cpu", "oom"], # list[str] -> dropped (blank in UI)
"organization_id": 42, # int -> stored OK
"mixed_list": [1, "two", 3.0], # mixed -> stored as the string "[1, 'two', 3.0]"
"nested_dict": {"a": [1, 2]}, # dict -> stored as the string "{'a': [1, 2]}"
},
)
```

Querying the log back (EAP `logs` dataset), the homogeneous scalar lists come back `null`, while the scalars and the *stringified* mixed/dict values are present.

### Root cause

`format_attribute` (sentry_sdk/utils.py:2125) preserves a **homogeneous** scalar `list`/`tuple` as a real array, but falls back to `safe_repr` (a string) for mixed lists and objects:

```python
elif isinstance(val, list):
ty = type(val[0])
if ty in (str, int, float, bool) and all(type(v) is ty for v in val):
return copy.deepcopy(val) # sent as a real array
...
return safe_repr(val) # everything else -> string
```

Sentry's log storage (EAP) only retains scalar attribute types (string / number / boolean), so the real arrays are dropped on ingestion. The net effect is counterintuitive: **homogeneous lists vanish, but mixed lists/objects survive (as strings).**

### Divergence from sentry-javascript

`@sentry/core` (v10.50) does the opposite for logs — `serializeAttributes(logAttributes, true)` runs with `fallback=true`, so **every** non-primitive (arrays and objects) is `JSON.stringify`'d into a string attribute and shows up. Its `attributes.js` even has an explicit comment that it intentionally does *not* send real arrays yet to avoid a future breaking change. So the same logging API gives different results across SDKs.

### Suggested fix

Make Python consistent with JS for now: stringify non-primitive attribute values (instead of sending homogeneous arrays that get dropped), or at minimum emit a debug log / drop-record when an attribute value can't be represented, so the loss isn't silent.

A docs note has been added in getsentry/sentry-docs#17921.

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