fix(server): идемпотентность upload, WAL, буфер ELM, таймаут LLM

- api/db.py: WAL mode, busy_timeout, request_id UNIQUE, close(), контекстный менеджер
- api/routes.py: проверка request_id при upload, /ping-llm кэш 60с, /chat через roles
- api/config.py: lru_cache на load()
- obd/protocol.py: reset_input_buffer перед _write(), условный READY в send()
- brain/client.py: модель 120b, таймаут из параметра, LLMError класс, обработка 429/5xx

api/db.py

@@ -18,10 +18,24 @@ from pathlib import Path
 class Database:
     def __init__(self, path: str | Path = "elmer.db"):
         self.path = Path(path)
-        self.conn = sqlite3.connect(str(self.path))
+        self.conn = sqlite3.connect(str(self.path), timeout=30, check_same_thread=False)
         self.conn.row_factory = sqlite3.Row
+        self.conn.execute("PRAGMA journal_mode=WAL")
+        self.conn.execute("PRAGMA busy_timeout=30000")
         self._init_schema()
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+        return False
+
+    def close(self):
+        if self.conn:
+            self.conn.close()
+            self.conn = None
+
     def _init_schema(self):
         self.conn.executescript("""
             CREATE TABLE IF NOT EXISTS cars (
@@ -113,22 +127,40 @@ class Database:
                 llm_success     INTEGER DEFAULT 0,
 
                 -- Сырые данные (JSON)
-                raw_responses   TEXT
+                raw_responses   TEXT,
+
+                -- Идемпотентность
+                request_id      TEXT UNIQUE,
+                response_json   TEXT
             );
 
-            CREATE INDEX IF NOT EXISTS idx_sessions_created ON sessions(created_at);
-            CREATE INDEX IF NOT EXISTS idx_sessions_vin    ON sessions(vin);
-            CREATE INDEX IF NOT EXISTS idx_sessions_mac    ON sessions(elm_mac);
-            CREATE INDEX IF NOT EXISTS idx_sessions_aid    ON sessions(android_id);
+            CREATE INDEX IF NOT EXISTS idx_sessions_created    ON sessions(created_at);
+            CREATE INDEX IF NOT EXISTS idx_sessions_vin        ON sessions(vin);
+            CREATE INDEX IF NOT EXISTS idx_sessions_mac        ON sessions(elm_mac);
+            CREATE INDEX IF NOT EXISTS idx_sessions_aid        ON sessions(android_id);
+            CREATE INDEX IF NOT EXISTS idx_sessions_request_id ON sessions(request_id);
         """)
         self.conn.commit()
 
     # ── sessions ──────────────────────────────────────────
 
+    def get_cached_response(self, request_id: str) -> dict | None:
+        """Возвращает сохранённый ответ сессии по request_id, или None."""
+        row = self.conn.execute(
+            "SELECT response_json FROM sessions WHERE request_id = ?", (request_id,)
+        ).fetchone()
+        if row and row["response_json"]:
+            return json.loads(row["response_json"])
+        return None
+
     def save_session(self, client_info: dict, responses: list[dict],
                      diagnosis: str = "", llm_model: str = "",
-                     llm_duration_ms: int = 0, llm_success: bool = False):
-        """Сохраняет сводную запись о сессии."""
+                     llm_duration_ms: int = 0, llm_success: bool = False,
+                     request_id: str = "", response_json: dict | None = None):
+        """Сохраняет сводную запись о сессии.
+
+        Если request_id передан и уже существует — silently return (идемпотентность).
+        """
         ci = client_info
 
         # Подсчёт DTC/PID из ответов
@@ -151,8 +183,10 @@ class Database:
                     vin = None
                 break
 
+        resp_json_str = json.dumps(response_json, ensure_ascii=False) if response_json else None
+
         self.conn.execute("""
-            INSERT INTO sessions (
+            INSERT OR IGNORE INTO sessions (
                 client_ip, real_ip, user_agent, content_length,
                 phone_model, phone_maker, android_version, android_sdk,
                 app_version, android_id,
@@ -163,9 +197,9 @@ class Database:
                 transport, mock_mode,
                 diagnosis_text, diagnosis_len, llm_model,
                 llm_duration_ms, llm_success,
-                raw_responses
+                raw_responses, request_id, response_json
             ) VALUES (?,?,?,?, ?,?,?,?, ?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,
-                      ?,?,?, ?,?, ?)
+                      ?,?,?, ?,?, ?,?,?)
         """, (
             ci.get("client_ip"), ci.get("real_ip"), ci.get("user_agent"),
             ci.get("content_length"),
@@ -179,6 +213,8 @@ class Database:
             diagnosis, len(diagnosis), llm_model,
             llm_duration_ms, 1 if llm_success else 0,
             json.dumps(responses, ensure_ascii=False) if responses else None,
+            request_id if request_id else None,
+            resp_json_str,
         ))
         self.conn.commit()