fix: resolve clippy pedantic warnings

[excoffierleonard]

• Replace lazy_static with std::sync::LazyLock
• Use case-insensitive file extension comparison in pptx parser
• Add missing #Errors doc section to parse function
• Merge identical match arms in ApiError implementations
• Move const declaration before statements in benchmark
• Use integer div_ceil instead of float arithmetic
• Remove unused lazy_static dependency