revert: remove accidental otel commit from main

Reverts only the 19 OTEL files from 5a7809a that ended up on main by
mistake. The unrelated chat UI / .codex changes that were bundled into
that commit are preserved on main; the OTEL work continues on the
marcode/otel-analytics-genesis worktree branch.

Author: tyulyukov

apps/landing/src/app/api/otel/traces/route.ts

@@ -1,23 +1,10 @@
-const REQUIRED_ENV_VARS = [
-  "JIRA_CLIENT_ID",
-  "JIRA_CLIENT_SECRET",
-  "OTEL_EXPORTER_OTLP_TRACES_ENDPOINT",
-] as const;
-
-const OPTIONAL_ENV_VARS = ["OTEL_EXPORTER_OTLP_TRACES_HEADERS"] as const;
+const REQUIRED_ENV_VARS = ["JIRA_CLIENT_ID", "JIRA_CLIENT_SECRET"] as const;
 
 export function validateEnv(): void {
   const missing = REQUIRED_ENV_VARS.filter((key) => !process.env[key]);
   if (missing.length > 0) {
     throw new Error(
-      `Missing required environment variables: ${missing.join(", ")}. Jira proxy and/or OTEL ingest will not function.`,
+      `Missing required environment variables: ${missing.join(", ")}. Jira proxy will not function.`,
     );
   }
-  for (const key of OPTIONAL_ENV_VARS) {
-    if (!process.env[key]) {
-      console.warn(
-        `[validateEnv] ${key} is not set. OTEL ingest will forward to Tempo without auth headers.`,
-      );
-    }
-  }
 }