feat(kei-buddy): wire OpenAiExtractor + chat_id whitelist + env-configurable LLM

Two additions on top of the MVP serve binary:

1. Whitelist by chat_id (KEI_BUDDY_ALLOWED_CHAT_IDS env, CSV).
   * BuddyContext gains Arc<Option<Vec<i64>>> allowed_chat_ids
   * chat_allowed() check fires before process_text
   * Non-whitelisted chats: warn-log + ignore (no response sent)
   * None or empty list = accept all (back-compat with prior behaviour)

2. Real LLM wiring (KEI_BUDDY_LLM_PROXY / _LLM_KEY / _LLM_MODEL).
   * When extractor-openai feature compiled in AND both proxy+key set,
     run_serve instantiates OpenAiExtractor instead of MockExtractor
   * Defaults: proxy=https://api.openai.com, key=OPENAI_API_KEY env,
     model=gpt-4o-mini
   * Fallback: warns + MockExtractor (state machine still walks, but
     LLM-extracted fields are empty)
   * extractor::OpenAiExtractor gains new_with_model(proxy, key, model);
     model is now per-instance instead of compile-time DEFAULT_MODEL

3. start_listener extracted as helper — keeps run_serve readable across
   the two feature-gated branches.

Verify-before-commit:
  * cargo check -p kei-buddy (default): PASS
  * cargo check -p kei-buddy --features extractor-openai: PASS
  * cargo test -p kei-buddy --lib: 20/0 unchanged

_primitives/_rust/kei-buddy/src/bin/kei-buddy.rs

@@ -48,10 +48,34 @@ async fn cmd_serve() -> anyhow::Result<()> {
         db_path: db_path_from_env(),
         bot_token: require_env("TELEGRAM_BOT_TOKEN")?,
         webhook_secret: require_env("TELEGRAM_WEBHOOK_SECRET")?,
+        allowed_chat_ids: allowed_chat_ids_from_env(),
+        llm_proxy_url: std::env::var("KEI_BUDDY_LLM_PROXY")
+            .ok()
+            .or_else(|| Some("https://api.openai.com".to_string())),
+        llm_api_key: std::env::var("KEI_BUDDY_LLM_KEY")
+            .ok()
+            .or_else(|| std::env::var("OPENAI_API_KEY").ok()),
+        llm_model: std::env::var("KEI_BUDDY_LLM_MODEL").ok(),
     };
     run_serve(cfg).await
 }
 
+/// Parse `KEI_BUDDY_ALLOWED_CHAT_IDS` CSV → Some(Vec<i64>); empty/missing → None.
+fn allowed_chat_ids_from_env() -> Option<Vec<i64>> {
+    let raw = std::env::var("KEI_BUDDY_ALLOWED_CHAT_IDS").ok()?;
+    let list: Vec<i64> = raw
+        .split(',')
+        .map(|s| s.trim())
+        .filter(|s| !s.is_empty())
+        .filter_map(|s| s.parse::<i64>().ok())
+        .collect();
+    if list.is_empty() {
+        None
+    } else {
+        Some(list)
+    }
+}
+
 #[cfg(not(feature = "serve"))]
 async fn cmd_serve() -> anyhow::Result<()> {
     anyhow::bail!("kei-buddy was compiled without the `serve` feature. Rebuild with --features serve.");

_primitives/_rust/kei-buddy/src/extractor.rs

@@ -140,14 +140,20 @@ pub mod openai {
     pub struct OpenAiExtractor {
         pub proxy_url: String,
         pub api_key: String,
+        pub model: String,
         client: reqwest::Client,
     }
 
     impl OpenAiExtractor {
         pub fn new(proxy_url: String, api_key: String) -> Self {
+            Self::new_with_model(proxy_url, api_key, DEFAULT_MODEL.to_string())
+        }
+
+        pub fn new_with_model(proxy_url: String, api_key: String, model: String) -> Self {
             Self {
                 proxy_url,
                 api_key,
+                model,
                 client: reqwest::Client::new(),
             }
         }
@@ -157,7 +163,7 @@ pub mod openai {
     impl LlmExtractor for OpenAiExtractor {
         async fn extract(&self, system: &str, user_text: &str) -> Result<Value, BuddyError> {
             let body = serde_json::json!({
-                "model": DEFAULT_MODEL,
+                "model": &self.model,
                 "temperature": 0,
                 "max_tokens": 200,
                 "messages": [

_primitives/_rust/kei-buddy/src/serve.rs

@@ -29,6 +29,15 @@ pub struct ServeConfig {
     pub db_path: String,
     pub bot_token: String,
     pub webhook_secret: String,
+    /// If `Some`, only these chat_ids are processed; others are warn-logged + ignored.
+    /// `None` (or empty) means accept all chat_ids.
+    pub allowed_chat_ids: Option<Vec<i64>>,
+    /// Optional OpenAI-compatible LLM proxy. If set together with `llm_api_key`,
+    /// `run_serve` instantiates `OpenAiExtractor`; otherwise falls back to
+    /// `MockExtractor` with a warning.
+    pub llm_proxy_url: Option<String>,
+    pub llm_api_key: Option<String>,
+    pub llm_model: Option<String>,
 }
 
 /// Axum state — implements `WebhookContext` for the webhook handler.
@@ -40,6 +49,8 @@ pub struct BuddyContext<E: LlmExtractor + Send + Sync + 'static> {
     pub store: Arc<SqliteBuddyStore>,
     pub extractor: Arc<E>,
     pub http: reqwest::Client,
+    /// Whitelist of chat_ids; `None` or empty = accept all.
+    pub allowed_chat_ids: Arc<Option<Vec<i64>>>,
 }
 
 impl<E: LlmExtractor + Send + Sync + 'static> Clone for BuddyContext<E> {
@@ -50,6 +61,7 @@ impl<E: LlmExtractor + Send + Sync + 'static> Clone for BuddyContext<E> {
             store: Arc::clone(&self.store),
             extractor: Arc::clone(&self.extractor),
             http: self.http.clone(),
+            allowed_chat_ids: Arc::clone(&self.allowed_chat_ids),
         }
     }
 }
@@ -73,7 +85,18 @@ impl<E: LlmExtractor + Send + Sync + 'static> WebhookContext for BuddyContext<E>
 }
 
 impl<E: LlmExtractor + Send + Sync + 'static> BuddyContext<E> {
+    fn chat_allowed(&self, chat_id: i64) -> bool {
+        match self.allowed_chat_ids.as_ref() {
+            Some(list) if !list.is_empty() => list.contains(&chat_id),
+            _ => true,
+        }
+    }
+
     async fn handle_text(&self, chat_id: i64, text: String) {
+        if !self.chat_allowed(chat_id) {
+            warn!(chat_id, "chat_id not in whitelist; ignoring");
+            return;
+        }
         if let Err(e) = self.process_text(chat_id, &text).await {
             error!(chat_id, error = %e, "failed to process text event");
         }
@@ -138,16 +161,48 @@ where
 pub async fn run_serve(cfg: ServeConfig) -> anyhow::Result<()> {
     init_tracing();
     let store = Arc::new(SqliteBuddyStore::from_path(&cfg.db_path)?);
+    let allowed_chat_ids = Arc::new(cfg.allowed_chat_ids);
+    let http = reqwest::Client::new();
+
+    #[cfg(feature = "extractor-openai")]
+    {
+        if let (Some(proxy), Some(key)) = (cfg.llm_proxy_url, cfg.llm_api_key) {
+            let model = cfg
+                .llm_model
+                .unwrap_or_else(|| "gpt-4o-mini".to_string());
+            tracing::info!(model = %model, "using OpenAiExtractor (LiteLLM-compatible)");
+            let extractor = Arc::new(crate::extractor::openai::OpenAiExtractor::new_with_model(
+                proxy, key, model,
+            ));
+            return start_listener(cfg.port, BuddyContext {
+                secret: cfg.webhook_secret,
+                bot_token: cfg.bot_token,
+                store,
+                extractor,
+                http,
+                allowed_chat_ids,
+            }).await;
+        }
+    }
+
+    warn!("no LLM extractor configured — using MockExtractor (state machine will advance but field-extraction returns empty)");
     let extractor = Arc::new(crate::extractor::MockExtractor::new(json!({})));
-    let ctx = BuddyContext {
+    start_listener(cfg.port, BuddyContext {
         secret: cfg.webhook_secret,
         bot_token: cfg.bot_token,
         store,
         extractor,
-        http: reqwest::Client::new(),
-    };
+        http,
+        allowed_chat_ids,
+    }).await
+}
+
+async fn start_listener<E>(port: u16, ctx: BuddyContext<E>) -> anyhow::Result<()>
+where
+    E: LlmExtractor + Send + Sync + 'static,
+{
     let router = build_router(ctx);
-    let addr = format!("0.0.0.0:{}", cfg.port);
+    let addr = format!("0.0.0.0:{}", port);
     let listener = tokio::net::TcpListener::bind(&addr).await?;
     tracing::info!(addr = %addr, "kei-buddy listening");
     axum::serve(listener, router).await?;