Dark mode images fix

[0xlukem]

📝 Description

This PR addresses some image and Mermaid diagram issues in dark mode.

🔍 Review Preference

Choose one:

• ✅ I have time to handle formatting/style feedback myself
• ⚡ Docs team handles formatting (check "Allow edits from maintainers")

🤖 AI-Ready Docs

If content changed, regenerate AI files:

• ✅ I ran python3 scripts/generate_llms.py
• ⚡ Docs team will regenerate (check "Allow edits from maintainers")

✅ Checklist

• Changes tested
• PaperMoon Style Guide followed

[Copilot]

Pull Request Overview

This PR addresses dark mode compatibility issues by removing white background fills from Mermaid diagrams and adding proper background styling to images that may not display well in dark mode.

• Updates Mermaid diagram styles to remove hard-coded white fill colors that cause visibility issues in dark mode
• Adds white background styling to images that need proper contrast in dark mode
• Regenerates AI-generated files to reflect the styling changes

Reviewed Changes

Copilot reviewed 19 out of 20 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
polkadot-protocol/smart-contract-basics/overview.md	Removes white fill from Mermaid diagram style attributes
polkadot-protocol/parachain-basics/blocks-transactions-fees/transactions.md	Adds white background styling to transaction lifecycle diagram
polkadot-protocol/architecture/polkadot-chain/overview.md	Adds white background styling to Polkadot architecture overview image
develop/smart-contracts/precompiles/index.md	Removes unused classDef styling from Mermaid diagram
develop/parachains/deployment/index.md	Removes white fill from deployment flowchart style attributes
develop/parachains/customize-parachain/overview.md	Adds white background and padding styling to FRAME overview image
llms-full.jsonl	Updates AI training data to reflect the styling changes
.ai/*	Regenerated AI files reflecting the updated content and styling changes

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