feat(@capacitor/local-notifications): Support `largeIcon` from local file/URI (file://, content://)

## Feature Request

### Plugin
`@capacitor/local-notifications`

### Description
On Android, the `largeIcon` option currently only supports referencing **drawable resource names** (e.g. `"icon_name"`). This makes it hard/impossible to show **dynamic images** in local notifications when those images are downloaded/user-specific and cached locally on the device (e.g. `file://...` paths or `content://...` URIs).

On iOS, similar use cases can be handled via `attachments` pointing to local file URLs. On Android, there is no equivalent way in the plugin to provide a local file/URI for `largeIcon` (or an expanded image style), even though the native Android notification API supports setting a bitmap via `NotificationCompat.Builder.setLargeIcon(Bitmap)`.

Related: ionic-team/capacitor-local-notifications#3

### Platform(s)
Android

### Preferred Solution
Add support for providing a local file path / URI for the notification large icon in a **backwards-compatible** way.

**Option A (backwards-compatible, no API change):**
Continue accepting `largeIcon: string`, but interpret it as:
- If `largeIcon` is a resource name (current behavior), resolve drawable by name.
- If `largeIcon` looks like a local path/URI:
- `file://...` or absolute `/...` path → decode bitmap from file path
- `content://...` → open stream via `ContentResolver` and decode bitmap
- call `NotificationCompat.Builder.setLargeIcon(bitmap)`

**Option B (explicit API):**
Introduce a new field (e.g. `largeIconPath` / `largeIconUrl`) for Android to avoid overloading semantics, while keeping existing `largeIcon` behavior as-is.

### Alternatives
- **Pre-bundle images as Android drawables** and reference them by name. This only works for static build-time assets and does not work for downloaded/dynamic images.

### Additional Context
Native implementation sketch (Android):

```kotlin
val value = largeIconString
val bmp: Bitmap? = when {
value.startsWith("content://") -> context.contentResolver
.openInputStream(Uri.parse(value))
?.use { BitmapFactory.decodeStream(it) }

value.startsWith("file://") -> BitmapFactory.decodeFile(Uri.parse(value).path)

value.startsWith("/") -> BitmapFactory.decodeFile(value)

else -> null
}

if (bmp != null) {
builder.setLargeIcon(bmp)
} else {
// existing behavior: resolve drawable by name
resolveDrawableByName(value)?.let { builder.setLargeIcon(it) }
}
````

Notes:

* Consider downsampling/scaling to avoid large allocations for big images.
* `content://` handling may require appropriate permissions depending on how the URI was obtained.

Related issue:

* ionic-team/capacitor-local-notifications#3