docs: Reorganize documentation on the webpage (#2651)

# What does this PR do?
Reorganizes the Llama stack webpage into more concise index pages,
introduce more of a workflow, and reduce repetition of content.

New nav structure so far based on #2637 

Further discussions in
https://github.com/meta-llama/llama-stack/discussions/2585

**Preview:**
![Screenshot 2025-07-09 at 2 31
53 PM](https://github.com/user-attachments/assets/4c1f3845-b328-4f12-9f20-3f09375007af)

You can also build a full local preview locally 

 **Feedback**
Looking for feedback on page titles and general feedback on the new
structure

**Follow up documentation**
I plan on reducing some sections and standardizing some terminology in a
follow up PR.
More discussions on that in
https://github.com/meta-llama/llama-stack/discussions/2585

docs/source/advanced_apis/post_training/remote_nvidia.md

@@ -0,0 +1,28 @@
+# remote::nvidia
+
+## Description
+
+NVIDIA's post-training provider for fine-tuning models on NVIDIA's platform.
+
+## Configuration
+
+| Field | Type | Required | Default | Description |
+|-------|------|----------|---------|-------------|
+| `api_key` | `str \| None` | No |  | The NVIDIA API key. |
+| `dataset_namespace` | `str \| None` | No | default | The NVIDIA dataset namespace. |
+| `project_id` | `str \| None` | No | test-example-model@v1 | The NVIDIA project ID. |
+| `customizer_url` | `str \| None` | No |  | Base URL for the NeMo Customizer API |
+| `timeout` | `<class 'int'>` | No | 300 | Timeout for the NVIDIA Post Training API |
+| `max_retries` | `<class 'int'>` | No | 3 | Maximum number of retries for the NVIDIA Post Training API |
+| `output_model_dir` | `<class 'str'>` | No | test-example-model@v1 | Directory to save the output model |
+
+## Sample Configuration
+
+```yaml
+api_key: ${env.NVIDIA_API_KEY:=}
+dataset_namespace: ${env.NVIDIA_DATASET_NAMESPACE:=default}
+project_id: ${env.NVIDIA_PROJECT_ID:=test-project}
+customizer_url: ${env.NVIDIA_CUSTOMIZER_URL:=http://nemo.test}
+
+```
+