Add configurable hardware startup splash

[PurpleSentinel]

What changed

• add a second startup splash containing board, processor, firmware, operating-system, and platform details
• configure both startup-screen durations independently in params.json, defaulting to two seconds
• migrate the legacy BOOT_DELAY_SEC value to the first-screen duration
• use high-contrast white text on black for the hardware screen
• preserve RP2040 framebuffer allocation order to avoid heap fragmentation
• document the new startup sequence and installation file

Why

The timer previously moved directly from the artwork splash to Ready and its single startup delay was not clearly named for a multi-screen sequence. The new information screen makes the installed hardware and runtime visible during boot. Physical testing also showed that dark text on the original background lacked sufficient contrast, so the final design uses white on black.

Impact

Existing configurations remain compatible. BOOT_DELAY_SEC is accepted as the first-screen duration, while the second screen defaults to two seconds. New configurations use STARTUP_SPLASH_DURATION_SEC and HARDWARE_SPLASH_DURATION_SEC.

Validation

• python -m unittest discover -s tests -v — 89 tests passed
• Python compilation and JSON validation passed
• git diff --check passed
• verified the rendered 240×240 framebuffer on the connected Waveshare RP2040-Touch-LCD-1.28
• verified a complete device boot on MicroPython 1.21.0 without a traceback

Closes#57