Rename project to lanshare in docs and code

[google-labs-jules]

Updated the project name in documentation and code to match Cargo.toml.

• README.md: Changed title from hello_world to lanshare.
• src/main.rs: Updated help text usage to lanshare.
• tests/e2e.rs: Updated temporary directory prefix to lanshare-e2e.

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PR created automatically by Jules for task 16687979334439683668 started by @jiang1997

[google-labs-jules]

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