ZB-H2-LED v1.5.4-beta [beta]

• chore(release): bump version to v1.5.4
• fix(zigbee): set coordinator dst addr in diag report config
• feat(renderer): C6 SSE segment push, last-value guards, export serializer
• fix(web): gate ota_image_type on target to support H2 and C6 builds
• feat(web): replace OTA polling with SSE push
• feat(web): add ota SSE topic and OTA status callback
• feat(config_api): add ota topic to SSE serializer
• fix: show updating status in system tab panel when in-progress
• fix: prevent OTA poll race, preserve S.ota on doOtaApply
• feat: show in-progress state in OTA banner and system tab
• chore: update beta OTA index for v1.5.3-beta