chore: migrate to start-sdk 2.0 and bump SimpleX Chat to 6.5.5

[helix-nine]

start-sdk 2.0 migration + SimpleX Chat 6.5.5

Migrates this package to @start9labs/start-sdk 2.0 (requires StartOS 0.4.0-beta.10) and bumps the bundled SimpleX Chat client from 6.5.4 to 6.5.5. Package version 0.2.0:1 → 0.2.1:0.

start-sdk 2.0 migration

• SDK pin → 2.0.1, TypeScript → ^6, tsconfig.json extends the shipped tsconfig.base.json, Makefile includes the SDK's s9pk.mk (vendored copy removed), reusable CI workflows repointed to Start9Labs/start-technologies.
• 2.0 API migrations as applicable: sdk.serviceInterface.* → sdk.host.* resolved over the LXC bridge, lazy SubContainer, alerts manifest field removed, and other ### Changed / ### Removed items from the SDK 2.0 changelog.

Upstream bump — SimpleX Chat 6.5.5

• images.simplex.source.dockerTag → lundog/simplex-chat:6.5.5 (multi-arch amd64 + arm64 confirmed on Docker Hub).
• Highlights from v6.5.5: initial support for supporter badges, and a fix for files without an extension being saved with a trailing dot. Patch-level upstream change; no state migration required.
• Release notes updated across all five locales in startos/versions/current.ts.

Test plan

• CI build is green (npm ci → tsc → SDK lint → ncc → s9pk pack).
• Install the built simplex-websocket-bridge_x86_64.s9pk on a StartOS 0.4.0-beta.10 server.
• Start the service; confirm it reaches its health check and its primary interface comes up.
• Configure/generate an API key and connect a WebSocket client through the bridge with the bearer token; confirm it can reach the headless SimpleX Chat client (send/receive a message).
• Confirm the running client reports SimpleX Chat 6.5.5.
• Upgrade path: install the prior 0.2.0/0.1.x build, then upgrade in place to 0.2.1:0; confirm existing profile/data volume (.simplex, media folder) survives and the service restarts healthy.

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