nessa: retire the API copy now served by nessa-api.freno.me

The Nessa API (nessaDb.*, nessa.community.*, Clerk auth and the Clerk user
webhook) lives in the Nessa repo's server/ on pan. This copy never served
the app: RemoteAPIClient wraps every input in {"input": …}, which the stock
tRPC adapter here reads as the input itself (queries 404, writes no-op).
Clerk's webhook already targets nessa-api.freno.me.

Drops the routers, nessa-auth, the webhook, NessaConnectionFactory, the
NESSA_* env and the now-unused @clerk/backend and svix. Nessa's marketing,
privacy and deletion pages stay.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -17,7 +17,6 @@
   "dependencies": {
     "@aws-sdk/client-s3": "^3.953.0",
     "@aws-sdk/s3-request-presigner": "^3.953.0",
-    "@clerk/backend": "^3.12.0",
     "@libsql/client": "^0.15.15",
     "@sentry/solidstart": "^10.67.0",
     "@solidjs/meta": "^0.29.4",
@@ -55,7 +54,6 @@
     "motion": "^12.23.26",
     "solid-js": "^1.9.5",
     "solid-tiptap": "^0.8.0",
-    "svix": "^1.98.0",
     "ua-parser-js": "^2.0.7",
     "uuid": "^13.0.0",
     "vinxi": "^0.5.7",