fix: Fix incorrect header image URL in README

[mondoreale]

This pull request updates documentation and metadata references throughout the codebase to point to the new streamr-dev/network repository, replacing outdated references to network-monorepo. The changes primarily affect README files, documentation, and code comments, ensuring consistency and accuracy for users and developers.

Repository and asset references:

• Updated all image and asset URLs in README.md files (packages/sdk/README.md, packages/node/README.md, packages/cli-tools/README.md, and root README.md) to point to the new repository structure and correct asset locations. [1] [2] [3] [4]

Documentation links:

• Changed all documentation links in markdown files (docs/docs/guides/use-any-language-or-device.md, docs/docs/usage/cli-tool.md, packages/node/plugins.md, packages/cli-tools/README.md) to reference the updated repository and directory structure. [1] [2] [3] [4] [5] [6]

Metadata updates:

• Updated the repository URL in packages/trackerless-network/package.json to point to the new GitHub repository.

Badge and social links:

• Fixed badge and social links in packages/sdk/README.md to reflect the new repository name.

Code comments:

• Updated a code comment in packages/node/src/broker.ts to reference the correct Wiki location.