fix: renew webOS Developer Mode without foregrounding the TV

[LucaXTech]

What changed

• replace ares-launch com.palmdts.devmode renewal with LG Developer Mode server API calls
• capture the 64-character Developer Mode session token once via ares-novacom during installation and store it with mode 0600
• check the session weekly and renew only below 14 days remaining
• remove the OnBootSec launch path that could bring the Developer Mode app to the foreground after a Raspberry Pi reboot
• update tests and documentation to enforce the silent renewal behavior

Physical validation

Validated on the configured LG TV from the Raspberry Pi:

• CheckDevModeSession.dev returned 999:41:59
• ResetDevModeSession.dev returned success / 200
• follow-up check returned 999:59:59
• the token was stored privately without printing it
• the installed silent helper later logged Developer Mode remaining: 999:57:56 and Renewal not required.
• the server-side renewal path does not launch the Developer Mode app on the TV