feat: add installable LG webOS TV client

[LucaXTech]

Implements the first testable UplinkWitness TV client for issue #20.

Scope:

• installable webOS web-app shell under clients/webos/
• LG launcher metadata plus 80x80 / 130x130 PNG icons
• first-run UplinkWitness server configuration persisted in localStorage
• fullscreen hosted wallboard loaded from the Raspberry/Linux host
• TV-first wallboard with Overview / Network / Router / Incidents sections
• directional remote navigation and Magic Remote click support
• ES5 / Chromium 53-safe implementation: no CSS Grid, JS modules, arrow functions, fetch, or CDN dependencies
• recoverable server settings via Magic Remote button
• packaging / Developer Mode install instructions
• regression tests for metadata, icon dimensions, launcher behavior and legacy-safe wallboard surface
• CI webOS packaging job that builds and uploads the exact .ipk artifact

Architecture decision: the IPK is deliberately a thin installable launcher while the actual TV UI is served by UplinkWitness on the monitored host. This keeps API requests same-origin, avoids unnecessary CORS exposure, and lets TV presentation updates follow the installed UplinkWitness host version rather than requiring a new IPK for every dashboard change.

Automated tests pass on Python 3.11 and 3.13, and the LG CLI successfully packages the v0.1 client as an all-architecture IPK in CI.

Do not merge until physical validation on the LG OLED55E8PLA is complete.

Closes #20 only after real TV install/launch/persistence/navigation validation succeeds.

[LucaXTech]

Physical validation completed successfully on LG OLED55E8PLA (webOS 4.x generation).

Validated on real hardware:

• launcher icon and fullscreen launch
• live wallboard data from the Raspberry Pi host
• Overview / Network / Router / Incidents sections
• directional remote navigation
• Magic Remote pointer/click interaction
• close/reopen behavior
• persisted server configuration
• server provisioning via ares-launch -p '{"server":"..."}'
• Developer Mode session renewal from the Raspberry Pi and weekly systemd timer
• final webOS-specific layout polish removing the observed tiny Overview vertical overflow

Final PR head: 66cd192.
Latest CI run passes. Physical validation gate is satisfied.