Add comprehensive documentation with i18n support (EN/BG)

- Add docs/ folder with English (en/) and Bulgarian (bg/) documentation
- Create index.md with language switching and links
- English docs: installation, quickstart, architecture, baraql, storage,
  schema, lsm, btree, vector, graph, fts, columnar, transactions,
  distributed, protocol, udf, api-binary, api-http, api-websocket
- Bulgarian docs: installation, quickstart, architecture, baraql,
  schema, lsm, btree, vector, graph, fts, transactions, distributed
- Update README license to BSD 3-Clause
- Add LICENSE file with BSD 3-Clause text

docs/bg/quickstart.md

@@ -0,0 +1,117 @@
+# BaraDB - Бързо Стартиране
+
+## Стартиране на Сървъра
+
+След компилация, стартирайте сървъра:
+
+```bash
+./build/baradadb
+```
+
+Сървърът ще стартира на `localhost:8080` по подразбиране.
+
+## Свързване чрез CLI
+
+BaraDB включва интерактивна конзола:
+
+```bash
+./build/baradadb --shell
+```
+
+## Основни Операции
+
+### Създаване на Схема
+
+```sql
+CREATE TYPE Person {
+  name: str,
+  age: int32
+};
+
+CREATE TYPE Movie {
+  title: str,
+  year: int32,
+  director: Person
+};
+```
+
+### Вмъкване на Данни
+
+```sql
+INSERT Person { name := 'Alice', age := 30 };
+INSERT Person { name := 'Bob', age := 25 };
+```
+
+### Заявки
+
+```sql
+SELECT name, age FROM Person WHERE age > 18;
+```
+
+### Обновяване
+
+```sql
+UPDATE Person SET age = 31 WHERE name = 'Alice';
+```
+
+### Изтриване
+
+```sql
+DELETE FROM Person WHERE name = 'Bob';
+```
+
+## Разширени Заявки
+
+### JOIN
+
+```sql
+SELECT u.name, o.total
+FROM users u
+INNER JOIN orders o ON u.id = o.user_id;
+```
+
+### Агрегати
+
+```sql
+SELECT department, count(*), avg(salary)
+FROM employees
+GROUP BY department
+HAVING count(*) > 5;
+```
+
+### CTEs
+
+```sql
+WITH active_users AS (
+  SELECT * FROM users WHERE active = true
+)
+SELECT * FROM active_users;
+```
+
+## Търсене на Вектори
+
+```sql
+-- Вмъкване с вектор
+INSERT vectors { id := 1, embedding := [0.1, 0.2, 0.3] };
+
+-- Търсене на подобни
+SELECT * FROM vectors ORDER BY cosine_distance(embedding, [0.1, 0.2, 0.3]) LIMIT 10;
+```
+
+## HTTP/REST API
+
+```bash
+# GET заявка
+curl http://localhost:8080/api/users
+
+# POST заявка
+curl -X POST http://localhost:8080/api/users \
+  -H "Content-Type: application/json" \
+  -d '{"name": "Alice", "age": 30}'
+```
+
+## Следващи Стъпки
+
+- [BaraQL Референция](bg/baraql.md)
+- [Схема](bg/schema.md)
+- [Архитектура](bg/architecture.md)