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/en/installation.md

@@ -0,0 +1,113 @@
+# BaraDB - Installation Guide
+
+## Requirements
+
+- **Nim Compiler** >= 2.0.0
+- **Operating System**: Linux, macOS, Windows
+
+## Installing Nim
+
+### Linux/macOS
+
+```bash
+curl https://nim-lang.org/choosenim/init.sh -sSf | sh
+```
+
+Or via package manager:
+
+```bash
+# Ubuntu/Debian
+apt-get install nim
+
+# macOS
+brew install nim
+```
+
+### Windows
+
+Download the installer from [nim-lang.org](https://nim-lang.org/install.html) or use winget:
+
+```powershell
+winget install nim
+```
+
+## Building BaraDB
+
+### Clone the Repository
+
+```bash
+git clone https://github.com/katehonz/barabaDB.git
+cd barabaDB
+```
+
+### Build the Project
+
+```bash
+# Debug build
+nim c -o:build/baradadb src/baradadb.nim
+
+# Release build (optimized)
+nim c -d:release -o:build/baradadb src/baradadb.nim
+```
+
+### Run Tests
+
+```bash
+nim c --path:src -r tests/test_all.nim
+```
+
+### Run Benchmarks
+
+```bash
+nim c -d:release -r benchmarks/bench_all.nim
+```
+
+## Installation Options
+
+### Pre-built Binary
+
+Download the latest release from the [GitHub Releases](https://github.com/katehonz/barabaDB/releases) page.
+
+### Docker
+
+```bash
+docker pull barabadb/barabadb
+docker run -it barabadb/barabadb
+```
+
+### Embedded Usage
+
+Add to your `.nimble` file:
+
+```nim
+requires "barabadb >= 1.0.0"
+```
+
+Then import in your code:
+
+```nim
+import barabadb
+
+var db = newLSMTree("./data")
+db.put("key1", cast[seq[byte]]("value1"))
+db.close()
+```
+
+## Verifying Installation
+
+```bash
+./build/baradadb --version
+```
+
+Expected output:
+
+```
+BaraDB v1.0.0
+multimodal database engine
+```
+
+## Next Steps
+
+- [Quick Start Guide](en/quickstart.md)
+- [Architecture Overview](en/architecture.md)
+- [BaraQL Query Language](en/baraql.md)