Implement automatic poll answer statistics tracking

Features:
- Add poll_mappings table to link Telegram poll_id with question_id
- Add PollStatisticsHandler to automatically record user votes
- Implement save_poll_mapping, get_question_id_by_poll methods
- Implement get_answer_id_by_option_index for answer lookup
- Update scheduler to save poll mappings on publish
- Add comprehensive test suite (test_statistics.py)
- Add STATISTICS_GUIDE.md with detailed documentation
- Update README.md with statistics features

Statistics features:
✅ Automatic vote counting for each answer option
✅ Percentage distribution display
✅ Anonymous tracking (no user data stored)
✅ View statistics via /manage → 📊 Statistics
✅ Support for multiple poll publications per question

All tests passing successfully!

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

game/database.py

@@ -104,6 +104,14 @@ class SQLiteWouldYouRatherRepository:
                     FOREIGN KEY (schedule_id) REFERENCES schedules(id) ON DELETE CASCADE,
                     UNIQUE (schedule_id, run_key)
                 );
+
+                CREATE TABLE IF NOT EXISTS poll_mappings (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    poll_id TEXT NOT NULL UNIQUE,
+                    question_id INTEGER NOT NULL,
+                    created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
+                    FOREIGN KEY (question_id) REFERENCES questions(id) ON DELETE CASCADE
+                );
                 """
             )
 
@@ -383,6 +391,39 @@ class SQLiteWouldYouRatherRepository:
             if deleted.rowcount == 0:
                 raise ValueError("Schedule does not exist.")
 
+    def save_poll_mapping(self, poll_id: str, question_id: int) -> None:
+        """Сохраняет связь между poll_id Telegram и question_id в базе."""
+        with self._connect() as connection:
+            connection.execute(
+                "INSERT OR REPLACE INTO poll_mappings(poll_id, question_id) VALUES (?, ?)",
+                (poll_id, question_id),
+            )
+
+    def get_question_id_by_poll(self, poll_id: str) -> int | None:
+        """Получает question_id по poll_id Telegram."""
+        with self._connect() as connection:
+            row = connection.execute(
+                "SELECT question_id FROM poll_mappings WHERE poll_id = ?",
+                (poll_id,),
+            ).fetchone()
+            return int(row["question_id"]) if row else None
+
+    def get_answer_id_by_option_index(
+        self, question_id: int, option_index: int
+    ) -> int | None:
+        """Получает answer_id по индексу опции в опросе."""
+        with self._connect() as connection:
+            row = connection.execute(
+                """
+                SELECT id FROM answers 
+                WHERE question_id = ? 
+                ORDER BY id 
+                LIMIT 1 OFFSET ?
+                """,
+                (question_id, option_index),
+            ).fetchone()
+            return int(row["id"]) if row else None
+
     def reset_used_flags(self) -> None:
         with self._connect() as connection:
             connection.execute("UPDATE questions SET used = 0")