Mechanical refactor and code cleanup iteration

[JanPetterMG]

This pull request continues the mechanical refactor and static-analysis cleanup pass across the firmware codebase.

The changes are mostly non-functional, but a few small correctness and robustness fixes are included where the cleanup exposed unsafe casts, wraparound-prone loops, or brittle string handling.

Key changes

• Standardizes static inline declaration order in headers.
• Replaces several C-string action checks with std::string_view comparisons.
• Removes the Home Assistant discovery ID regex dependency and uses a fixed discovery component ID instead.
• Adds explicit casts and targeted NOLINT annotations where conversions are intentional.
• Uses lroundf() instead of roundf() followed by integer casts for weather and thermometer values.
• Fixes loop bounds that could be flagged as wraparound-prone when iterating over uint8_t-sized ranges.
• Cleans up mode internals, including naming in PixelSequenceMode, draw-coordinate casts, and branch-clone suppressions.
• Refactors MetaballsMode::handle() to reduce nesting and make the microphone guard an early return.
• Improves metaballs brightness accumulation by using a wider intermediate type before clamping to UINT8_MAX.
• Updates ellipse drawing to use hypotf(), clearer pitch-ratio calculations, and correct row/column bounds.
• Adjusts CircleMode radius calculation and drawing so the effect better reflects the display geometry.
• Avoids passing raw std::string_view::data() to Server-Sent Events by materializing a null-terminated string first.

Impact

This should reduce static-analysis noise and make the affected code easier to read and maintain without changing the public API or configuration format.

The main behavior-adjacent changes are limited to safer rendering/math internals, more robust action parsing, and corrected display geometry handling.