Convert TimezoneDB to Keel (host + packs)

[LizAinslie]

Parent: #810

Ask

Rebuild / migrate TimezoneDB’s web (and relevant surfaces) onto Keel: Ktor host owns routes/page ids/seed; UI as Vite .feb packs at render time.

Context

• Current stack: Kotlin/Ktor API + Vue web + webext/powercord platforms (see README)
• Keel product locks: call-site pack ref, pack-authored head, visits non-SEO, Harbor is testbench only
• Docs: https://keel.kolektiv.computer

Acceptance sketch

• Host uses Keel page registry + respondPage(pack, seed)
• Primary web UI is a Keel pack (adapter TBD)
• Extensions still consume the API/contract (may stay non-Keel clients initially)
• Migration notes in DEVELOPING / docs

Out of scope

Blind Dependabot majors — track under toolchain issue.

[LizAinslie]

Path lock from Mey:

1. Cutover: Keel host + keep current Vue for the move.
2. Later UI modernize: switch to the smallest Keel adapter that has a full test suite (Lit/Preact are size candidates only once their Keel tests are green). Do not promise Lit/Preact until tests exist.