Improve middleware feature

[iazaran]

Description

This PR improves the dashboard UX and documentation with two changes:

1. Changes the default date filter from "All Time" to "Today" for better performance when viewing the traces list
2. Moves the middleware setup documentation to immediately after the installation steps, making it more discoverable as a recommended setup step

Changes Made

• Changed default date filter to "Today" instead of "All Time" for better query performance on large datasets
• Reordered date filter dropdown from shortest to longest time period (Last Hour → Today → Yesterday → Last 7 Days → Last 30 Days → All Time)
• Fixed bug where selecting "All Time" would revert back to "Today" (changed value from empty string to "all")
• Added "Recommended: Enable HTTP Middleware" section after installation steps in README.md and docs/index.html
• Removed duplicate middleware documentation that was previously in a separate "Auto HTTP Ingestion" section

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Related Issues

N/A - Improvements discovered during real-world usage testing