🐛 Bug Report: Execution.fromMap throws Bad state: No element when server doesn't return resourceType (pre-Sites servers

### 👟 Reproduction steps

Since `appwrite: 26.0.0`, `Execution.fromMap` (in `lib/src/models/execution.dart`) parses the [resourceType](url) field like this:

```dart
resourceType: enums.ExecutionResourceType.values.firstWhere(
(e) => e.value == map['resourceType'],
),
```

This throws Bad state: No element on any self-hosted Appwrite server that predates the Functions/Sites unification and therefore doesn't send a resourceType field in the execution response — it still returns the older shape with functionId instead of resourceId/resourceType.

Because firstWhere has no orElse, this crashes on every Functions.createExecution() / Functions.getExecution() / Functions.listExecutions() call against such a server, even though the HTTP call itself succeeds (2xx) and the function executes correctly — the data is simply lost because the SDK can't build the Execution model from a valid response.

To Reproduce

1. Point the SDK at a self-hosted Appwrite server running a version prior to the Functions/Sites unification (i.e. one that still returns functionId on executions instead of resourceId + resourceType).
2. Call Functions.createExecution(...).
3. The function executes successfully server-side, but the SDK throws:

```
Bad state: No element
#0 ListBase.firstWhere (dart:collection/list.dart:132:5)
#1 new Execution.fromMap (package:appwrite/src/models/execution.dart:92:56)
#2 Functions.createExecution (package:appwrite/services/functions.dart:81:29)
```

Raw response for such an execution (obtained via the REST API directly) looks like:

{
"$id": "...",
"functionId": "test-function-id",
"trigger": "http",
"status": "completed",
"responseStatusCode": 200,
"responseBody": "...",
...
}

Note the absence of resourceId / resourceType.

### 👍 Expected behavior

The SDK shouldn't hard-crash when the server predates a schema change. At minimum, resourceType should fall back to a sane default (e.g. functions, inferred from the presence of the legacy functionId field) instead of throwing, so callers can still get responseBody/status/etc. Ideally the SDK would also surface a clear version-mismatch error rather than an opaque Bad state: No element.

### 👎 Actual Behavior

It throw an error

### 🎲 Appwrite version

Appwrite Cloud

### 💻 Operating system

Linux

### 🧱 Your Environment

- appwrite (Dart/Flutter SDK): 26.0.0
- Platform: Flutter, iOS/Android
- Server: self-hosted Appwrite (pre-Sites-unification version)

### 👀 Have you spent some time to check if this issue has been raised before?

- [x] I checked and didn't find similar issue

### 🏢 Have you read the Code of Conduct?

- [x] I have read the [Code of Conduct](https://github.com/appwrite/appwrite/blob/HEAD/CODE_OF_CONDUCT.md)

Start in lib/src/models/execution.dart and trace how Functions.createExecution(), Functions.getExecution(), and Functions.listExecutions() construct Execution from legacy responses. Compare the resourceType/resourceId fields with the older functionId response shape; done means these calls no longer throw and still expose the execution status, response body, and other returned data.

Written by the indexing model from the issue text.