[Doc][Misc] Refactor and simplify DeepSeek-V3.2 deployment documentation (vllm-project#12676)

### What this PR does / why we need it?
This PR refactors and improves the DeepSeek-V3.2 deployment tutorial.
Specifically, it:
- Adds section numbering to all major headings for better readability
and structure.
- Simplifies the "Prefill-Decode Disaggregation" section by linking to
the official `launch_online_dp.py` script instead of embedding the
entire Python code.
- Introduces a parameter description table for the launch script.
- Organizes node-specific shell templates using tabbed markdown blocks
(`=== "Node..."`).
- Adds a new FAQ section pointing to the public FAQ page.

### Does this PR introduce _any_ user-facing change?
No, this is a documentation-only update.

### How was this patch tested?
Tested by verifying the markdown rendering and ensuring all links and
commands are correct.


- vLLM version: v0.25.1
- vLLM main:
vllm-project/vllm@fe784ff

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Signed-off-by: wangzhishenghw <wangzhisheng6@h-partners.com>

Author: wangzhishenghw