Lights: fix broken unsigned arithmetic + refactoring

[mcspr]

• replace unsigned return values with the signed ones to avoid undefined behaviour when mixing signed and unsigned in one expression or accidentally casting negative values to unsigned (like lightBrightness(...), lightChannel(id, ...), causing value to become 100% when the intent was to set it to 0%)
• update encoder configure method to only configure encoder objects once, on boot. should be cleaned-up anyway for runtime pin config, either requiring reboot re-using existing objects when nothing had changed.
  fixes Xiaomi Desklamp Rotary Encoder Bugs #1934

some related changes

• clean-up adjustment code for terminal, reuse same code for mqtt and http api
• clean-up lights code casting const char * back to char * when parsing using strtok, use local stack buffer with memmove strncpy
• update toCSV to use the same logic as the other methods, slightly smaller code size. and a small fix for mqtt groups never allowing values to increase (should be properly fixed later with brightness sent separately and maybe the same settings as relay groups)
• update comms masks usage, move hardcoded values to the header as named variables
• move declarations outside of the prototypes header