Add first kotlintoolchain version

[singleton11]

No description provided.

[chloe41427]

Reviewed the migration end-to-end against the patterns used elsewhere in the repo (BallerinaMigrations, KobwebMigrations, etc.) and against package.scala's validation rules.

What's correct

• Order/id wiring — order = "002" cleanly follows 001; id 002_add_kotlintoolchain_0_11_0 matches the NNN_add_<candidate>_<version> convention used across other candidates, and the author is consistent with 001.
• Candidate reference — candidate = "kotlintoolchain" matches the candidate inserted in migration001.
• Version length — "0.11.0" (6 chars) is well under the 15-char ceiling enforced by versionValidation.validVersion in package.scala.
• URL — https://packages.jetbrains.team/.../kotlin-cli-sdkman-0.11.0.zip resolves with HTTP/2 200 (13,158 bytes), so .validate() will succeed at migration time.
• Platform default — relying on Universal (default) is consistent with the distribution = "UNIVERSAL" set on the candidate in migration001, and matches how other UNIVERSAL candidates (e.g. Kobweb when they add their first version) are wired.
• .asCandidateDefault() — required for the first version; without it candidates.default would stay None and the CLI wouldn't have a default to install. Correct here.
• CI — build job is green.

Nits (non-blocking)

• Tiny style drift: migration001 is def migration001(implicit db: MongoDatabase) = while migration002 is def migration002(implicit db: MongoDatabase): Unit =. Both forms exist across the codebase, so not worth churning — just flagging.
• Some files (e.g. BallerinaMigrations) extract private val CandidateName = "kotlintoolchain" to avoid repeating the string. Optional; the file is small enough that inline is fine.

LGTM — first version is correctly wired and validated.