fix: migrate LVGL 8 API calls to LVGL 9

[pfefferle]

Summary

ESPHome 2026.4.0 upgraded the bundled LVGL from 8.x to 9.x, which is a breaking API change. The Tab5 scripts currently fail to compile against the new LVGL version with errors like:

error: too few arguments to function 'void lv_canvas_set_px(lv_obj_t*, int32_t, int32_t, lv_color_t, lv_opa_t)'
error: invalid conversion from 'void*' to 'lv_obj_t*'

This PR migrates the affected calls to the LVGL 9 API:

• lv_canvas_set_px — added the now-required lv_opa_t opacity argument (LV_OPA_COVER for the existing fully-opaque behavior).
• lv_event_get_target — switched to lv_event_get_target_obj, the LVGL-9-native typed helper. The old name now returns void * because the target isn't always an lv_obj_t anymore.
• lv_obj_clear_flag / lv_obj_clear_state — renamed to lv_obj_remove_flag / lv_obj_remove_state. The old names still work via compat wrappers but were renamed in LVGL 9 and may be dropped in future ESPHome releases.

Files touched:

• common/tab5-scripts.yaml
• common/tab5-ha-hmi.yaml

No behavioral change — pure API migration.

Test plan

• Build the m5stack-tab5 example against ESPHome 2026.4.0+ and confirm it compiles.
• Flash to a Tab5 and verify the color palette indicator (uses lv_event_get_target_obj and lv_canvas_set_px) still tracks touch input and updates the selected color.
• Verify the AC HMI panel still enables/disables correctly when the bound entity becomes unavailable (exercises the lv_obj_remove_flag / lv_obj_remove_state paths).