Negative `INTERVAL` offsets in RANGE window frames are accepted and panic at execution

### Describe the bug

ROWS and GROUPS frame offsets are parsed as `UInt64`, so `ROWS BETWEEN -1 PRECEDING ...` is a planning error ("frame offsets for ROWS / GROUPS must be non negative integers"). RANGE offsets are kept as strings until `coerce_window_frame` (`datafusion/optimizer/src/analyzer/type_coercion.rs`) casts them to the ORDER BY type, and an interval literal such as `INTERVAL '-1 day'` carries its sign inside the string, so a negative RANGE offset is never rejected.

The frame then starts after it ends. The window execution code assumes `start <= end` and panics in debug builds:

### To Reproduce

Debug build of `datafusion-cli`:

```sql
SELECT count(*) OVER (ORDER BY x RANGE BETWEEN INTERVAL '-1 month' PRECEDING AND CURRENT ROW)
FROM (VALUES (arrow_cast(1, 'Timestamp(Second, None)')), (arrow_cast(2, 'Timestamp(Second, None)'))) t(x);
```

```text
thread 'main' panicked at datafusion/physical-expr/src/window/sliding_aggregate.rs:216:33:
attempt to subtract with overflow
```

```sql
SELECT count(*) OVER (ORDER BY x RANGE BETWEEN INTERVAL '-1 day' PRECEDING AND INTERVAL '-1 day' FOLLOWING)
FROM (VALUES (now()), (now())) t(x);
```

```text
thread 'main' panicked at datafusion/expr/src/window_state.rs:65:18:
attempt to subtract with overflow
```

In release builds the same queries do not panic but return wrong results (e.g. `count(*)` of 0 for every row over three consecutive dates with `INTERVAL '-1 day' PRECEDING`).

### Expected behavior

A planning error, consistent with ROWS / GROUPS (and with PostgreSQL, which rejects the frame with "frame starting offset must not be negative").

### Additional context

Found while running a corpus of extreme-value literals against a debug build of `datafusion-cli`.

Reproduce the queries with a debug build of datafusion-cli, then inspect coerce_window_frame in datafusion/optimizer/src/analyzer/type_coercion.rs. Trace the resulting frame through datafusion/physical-expr/src/window/sliding_aggregate.rs and datafusion/expr/src/window_state.rs. Done means negative RANGE INTERVAL offsets produce a planning error like ROWS and GROUPS instead of reaching execution or returning incorrect results.

Written by the indexing model from the issue text.