docs(readme): restructure for beginner clarity and expand API sections

[DeepKnowledge1]

📝 Description

Restructured README for beginner clarity — the previous version mixed install
options, Python API, CLI, and REST API under a single Quickstart heading with
no clear path for a first-time user.

• Reorganised Quickstart into a linear 4-step flow (install → dataset → train → detect)
• Replaced parallel install options (A/B/C) with one linear path, GPU as a one-liner
• Added dataset folder structure and MVTec download command before any code runs
• Moved Python API, REST API, and Tasks & Modes into their own named sections
• Expanded Python API into an annotated single block with step headers and output shape comments
• Added REST API server-start context that was previously missing
• Wrapped Python API and REST API in <details> collapsible blocks
• Restored Tasks & Modes table and per-category MVTec breakdown that were dropped

🔄 Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📖 Documentation update
• 🏗️ Infrastructure / CI/CD update

🧪 Hardware & Matrix Testing

I have successfully built and tested this code using uv on:

• anomavision[cpu] (Standard/Edge)
• anomavision[cu121] (CUDA 12.1)
• anomavision[cu124] (CUDA 12.4)
• anomavision[cu118] (CUDA 11.8)

Documentation-only change — no code was modified, hardware testing not applicable.

Host OS used for testing:

• Linux / Ubuntu
• Windows (Native or WSL2)
• macOS

✅ Developer Checklist

• My code follows the core style guidelines of this project (Ruff/Black formatting).
• I have run uv run pytest and all unit tests pass locally.
• Lockfile Guard: If I added or modified a dependency in pyproject.toml, I have run uv lock --python 3.10 and committed the updated uv.lock file.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the documentation accordingly (if applicable).

📸 Screenshots / Visual Proof (Optional)