auth: switch to Authentik OAuth for LLM API

- Add lib/auth.ts: OAuth client with token caching
- Use client_credentials grant with portfolio-agent service account
- Mount portfolio-agent-oidc secret for credentials
- Remove static LLM_API_TOKEN dependency

app/api/chat/route.ts

@@ -1,7 +1,8 @@
 import { NextRequest } from 'next/server'
+import { getAccessToken } from '@/lib/auth'
 
-const LLM_API_URL = 'http://api-gateway.api.svc.cluster.local:8080/v1/chat/completions'
-const MODEL = 'reasoning'
+const LLM_API_URL = process.env.LLM_API_URL || 'http://api-gateway.api.svc.cluster.local:8080/v1/chat/completions'
+const MODEL = process.env.LLM_MODEL || 'reasoning'
 
 const SYSTEM_PROMPT = `You are **Poimen**, Rock Liang's AI assistant embedded in his portfolio. You help visitors understand Rock's journey, technical depth, and what drives him. Speak with a humble, curious tone—Rock is someone who learns by building, breaks things to understand them, and is genuinely excited about distributed systems and AI.
 
@@ -134,16 +135,9 @@ GOOD example:
 BAD: "Rock resolved the Terraform configuration drift issue by implementing automated drift detection and real-time visibility into discrepancies..." — this is garbage. Never do this.`
 
 export async function POST(request: NextRequest) {
-  const token = process.env.LLM_API_TOKEN
-
-  if (!token) {
-    return new Response(
-      JSON.stringify({ error: 'LLM_API_TOKEN not configured' }),
-      { status: 500, headers: { 'Content-Type': 'application/json' } }
-    )
-  }
-
   try {
+    // Get OAuth token (cached, auto-refreshes)
+    const token = await getAccessToken()
     const { message } = await request.json()
 
     const response = await fetch(LLM_API_URL, {

infra/portfolio/base/deployment.yaml

@@ -26,11 +26,22 @@ spec:
             secretKeyRef:
               name: portfolio-secrets
               key: FORGEJO_TOKEN
-        - name: LLM_API_TOKEN
+        # OAuth credentials for LLM API (client_credentials grant)
+        - name: AUTHENTIK_CLIENT_ID
           valueFrom:
             secretKeyRef:
-              name: portfolio-secrets
-              key: LLM_API_TOKEN
+              name: portfolio-agent-oidc
+              key: CLIENT_ID
+        - name: AUTHENTIK_CLIENT_SECRET
+          valueFrom:
+            secretKeyRef:
+              name: portfolio-agent-oidc
+              key: CLIENT_SECRET
+        - name: AUTHENTIK_TOKEN_URL
+          valueFrom:
+            secretKeyRef:
+              name: portfolio-agent-oidc
+              key: TOKEN_URL
         ports:
         - name: http
           containerPort: 3000

lib/auth.ts

@@ -0,0 +1,65 @@
+/**
+ * Authentik OAuth client for service account authentication.
+ * Uses client_credentials grant with token caching.
+ */
+
+interface TokenResponse {
+  access_token: string
+  token_type: string
+  expires_in: number
+}
+
+interface CachedToken {
+  token: string
+  expiresAt: number
+}
+
+let cachedToken: CachedToken | null = null
+
+/**
+ * Get a valid access token, fetching a new one if expired.
+ * Tokens are cached with 60s buffer before expiry.
+ */
+export async function getAccessToken(): Promise<string> {
+  const now = Date.now()
+  
+  // Return cached token if still valid (with 60s buffer)
+  if (cachedToken && cachedToken.expiresAt > now + 60000) {
+    return cachedToken.token
+  }
+
+  const clientId = process.env.AUTHENTIK_CLIENT_ID
+  const clientSecret = process.env.AUTHENTIK_CLIENT_SECRET
+  const tokenUrl = process.env.AUTHENTIK_TOKEN_URL || 'https://authentik.riotpiao.com/application/o/token/'
+
+  if (!clientId || !clientSecret) {
+    throw new Error('AUTHENTIK_CLIENT_ID and AUTHENTIK_CLIENT_SECRET must be set')
+  }
+
+  const response = await fetch(tokenUrl, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/x-www-form-urlencoded',
+    },
+    body: new URLSearchParams({
+      grant_type: 'client_credentials',
+      client_id: clientId,
+      client_secret: clientSecret,
+      scope: 'openid roles',
+    }),
+  })
+
+  if (!response.ok) {
+    const error = await response.text()
+    throw new Error(`Failed to get access token: ${response.status} - ${error}`)
+  }
+
+  const data: TokenResponse = await response.json()
+  
+  cachedToken = {
+    token: data.access_token,
+    expiresAt: now + (data.expires_in * 1000),
+  }
+
+  return cachedToken.token
+}