fix(web): fully remove payload runtime from production build

Remove ALL Payload imports, withPayload wrapper, and (payload)
routes. Blog index + changelog are now static data arrays.
Blog post at /blog/peer-messaging-claude-code is static TSX.

Payload CMS stays as a dev dependency for future local admin
but has zero presence in the production build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/db/migrations/0003_add-presence-summary.sql

@@ -0,0 +1 @@
+ALTER TABLE "mesh"."presence" ADD COLUMN "summary" text;