refactor: reorganize thematic groups and reorder sections within groups

Restructures the top-level ToC groups for better logical cohesion:
- Split 'Web & API' into 'Web' (frameworks, servers, CMS) and
  'HTTP & Scraping' (clients, scraping, URL, email)
- Move 'Database & Storage' earlier in the ToC, before 'Data & Science'
- Merge 'Web Content Extraction' and 'Web Crawling' into a single
  'Web Scraping' section
- Rename 'Content & Media' to 'Text & Documents' and 'Media' (split)
- Rename 'System & Runtime' to 'Python Language' and 'Python Toolchain'
- Rename 'Security & Auth' to 'Security'; move Authentication to Web group
- Rename 'Development Tools' to 'Developer Tools', 'DevOps & Infrastructure' to 'DevOps'
- Reorder sections within groups to reflect learning progression
  (e.g., Deep Learning before Machine Learning in AI & ML)
- Move Hardware and Microsoft Windows to Miscellaneous group
- Add s3cmd to DevOps and youtube-dl to Command-line Tools
- Update CONTRIBUTING.md example group names to match new labels

Co-Authored-By: Claude <noreply@anthropic.com>

CONTRIBUTING.md

@@ -80,7 +80,7 @@ Use the **PyPI package name** as the display name so developers can copy it dire
 ## Adding a New Section
 
 1. Add section description in italics: `*Libraries for doing X.*`
-2. Add the section under the appropriate thematic group (e.g., **AI & ML**, **Web & API**)
+2. Add the section under the appropriate thematic group (e.g., **AI & ML**, **Web**, **Data & Science**)
 3. Add the section title to the Table of Contents under its group
 4. Keep entries in alphabetical order within each category