feat(mcp): Streamable HTTP transport + deploy; secure restoreRevision

- apps/mcp/src/http.ts: serve MCP over Streamable HTTP (MCP 2025-03-26) on
  :4021, stateless mode (sessionIdGenerator undefined), CORS on /mcp. Remote
  clients can now call the 6 tools + 4 resources without a stdio subprocess.
- deploy/mcpedia-mcp.service: supervised systemd unit (MCP_PORT=4021).
- Caddy: mcp.asepharyana.my.id -> 4021; wiki. domain now also routes /trpc/*
  to the API (was swallowed by web -> tRPC was unreachable on the domain).
- apps/api: restoreRevision tRPC mutation now requires x-webhook-secret (the
  Web UI calls @mcpedia/core directly, so this only gates the open network
  endpoint). Threads the header into tRPC Context. Secures a state-changing
  action that was anonymously callable.
Verified live: https://mcp.asepharyana.my.id/mcp initialize/tools/list/
resources/list all 200; restoreRevision no-secret -> unauthorized, with-secret
-> handler; read-only tRPC reachable via domain.

apps/api/src/trpc.ts

@@ -3,6 +3,10 @@ import { db } from "@mcpedia/db";
 
 export interface Context {
   db: typeof db;
+  // Raw `x-webhook-secret` header from the incoming request, if present.
+  // State-changing tRPC mutations (restoreRevision) require it to match
+  // WEBHOOK_SECRET; read-only procedures ignore it.
+  webhookSecret?: string;
 }
 
 export const t = initTRPC.context<Context>().create();