dx serve to respect tailwind_input

**Problem**
`dx serve` does not respect `tailwind_input` param in Dioxus.toml

currently it is hardcoded all over the code https://github.com/DioxusLabs/dioxus/blob/main/packages/cli/src/tailwind.rs

**Environment:**

- Dioxus version: 0.71
- Rust version: 1.91.1 (ed61e7d7e 2025-11-07)
- OS info: linux mint
- App platform: desktop

Start in packages/cli/src/tailwind.rs, then trace how dx serve reads Dioxus.toml and handles the tailwind_input parameter. Confirm where the input path is currently hardcoded. Done means dx serve uses the configured tailwind_input value instead of the hardcoded path, including for the desktop environment described in the issue.

Written by the indexing model from the issue text.