Add per-profile SOCD cleaning settings to address #1187

[j-zhao]

Addresses the SOCD portion of #1187.

Full disclosure, this was specced out with Claude Fable, with first initial review by myself.

Summary

Each profile can now override the global SOCD cleaning mode. A profile without an override uses the global setting, exactly as before. The Pin Mapping page gets a per-profile SOCD dropdown.

• New proto message ProfileSettings { socdEnabled, socdMode } as GpioMappings.settings (field 5; field 4 stays reserved for feat: Add per-profile keyboard mapping and per-pin GPIO polarity support #1566). socdEnabled == false means "use the global setting".
• Resolution order: SOCD slider add-on (hardware) > profile override > global. The bypass-to-neutral guard for PS3/Switch/NeoGeo/PS4 is unchanged.
• SOCD hotkeys and the on-device display menu write to the effective source: the profile when its override is active, the global otherwise. Neither ever creates an override, and neither touches overrides while the slider add-on owns the mode.
• Web API: the pin-mapping and profile endpoints carry socdEnabled/socdMode. Setters apply the keys only when present and in range, so older payloads leave stored overrides unchanged. getProfileOptions JSON capacity grows 500 -> 700 slots (the old budget overflowed at 4+ profiles with the new keys).

Web server fix

On-device testing exposed a latent webconfig bug: API responses are heap strings freed on connection close, but lwIP's httpd queues data by reference (assuming ROM), so a freed buffer can hit the wire as garbage. Fixed by setting HTTP_IS_DATA_VOLATILE to TCP_WRITE_FLAG_COPY in lib/lwip-port/lwipopts.h. This may also fix rare corrupted webconfig responses on current firmware.

Design notes

• Allow SOCD settings to be stored alongside a Profile #1187 suggested ProfileOptions, but profile 1 lives outside it (config.gpioMappings), so the settings nest under GpioMappings to give every profile the same shape.
• New/copied profiles inherit the source profile's SOCD override, matching how pins and labels copy.
• Compatibility: old configs behave identically (override defaults off); downgrade is safe (unknown field is skipped); Config_size 21267 -> 21303 (+36 bytes, budget 32756); no migration.

Testing

CI: all boards compile (fork run). Local: nanopb regen, npm run build-proto, npx vite build.

On-device checklist:

• Profile switch changes effective SOCD (display widget confirms).
• Hotkey writes the profile when overridden, else the global.
• Slider wins over an overridden profile.
• Settings survive reboot and backup/restore; restoring a pre-feature backup preserves overrides.
• Web UI round-trips "Use Global" and each mode for all profiles; Pin Mapping loads with zero alternative profiles.
• OLED menu shows the effective mode under an override; a menu edit changes the override, not the global.
• A menu session changing both profile and SOCD mode writes the mode to the newly selected profile.