docs: expand README and documentation for production release

- Update README.md status from 'educational proof-of-concept' to 'production-ready'
- Fix binary size: 286KB -> 3.3MB
- Update test count: 162/35 -> 262/56
- Add sections: benchmarks, Docker, clients, security, config, monitoring, backup, cross-modal queries, troubleshooting
- Expand project structure with all 49 modules and ~14,100 LOC
- Add 10 new docs: performance, deployment, configuration, clients, security, monitoring, backup, crossmodal, troubleshooting, changelog
- Expand docs/en: architecture, baraql, installation, protocol
- Update docs/bg: architecture, installation
- Update docs/index.md with new links
- Update .gitignore for __pycache__, rust/target, nim binaries

docs/en/backup.md

@@ -0,0 +1,191 @@
+# Backup & Recovery
+
+## Online Snapshots
+
+BaraDB supports online snapshots without stopping the server. The snapshot
+captures a consistent point-in-time view using MVCC.
+
+### Creating a Snapshot
+
+```nim
+import barabadb/core/backup
+
+var bm = newBackupManager()
+bm.createSnapshot("/backup/baradb_2025-01-15")
+```
+
+### Via CLI
+
+```bash
+./build/baradadb --snapshot --output=/backup/snapshot.db
+```
+
+### Via HTTP API
+
+```bash
+curl -X POST http://localhost:8080/api/backup \
+  -H "Content-Type: application/json" \
+  -d '{"destination": "/backup/snapshot.db"}'
+```
+
+### Automated Backups
+
+Use cron for scheduled backups:
+
+```bash
+# Daily snapshot at 2 AM
+0 2 * * * /usr/local/bin/baradadb --snapshot --output=/backup/baradb_$(date +\%Y\%m\%d).db
+
+# Keep last 7 days
+find /backup -name "baradb_*.db" -mtime +7 -delete
+```
+
+## Point-in-Time Recovery (PITR)
+
+BaraDB uses the Write-Ahead Log (WAL) for point-in-time recovery.
+
+### WAL Archiving
+
+Enable continuous WAL archiving:
+
+```bash
+BARADB_WAL_ARCHIVE_DIR=/backup/wal \
+BARADB_WAL_ARCHIVE_INTERVAL_MS=60000 \
+./build/baradadb
+```
+
+### Recovery from Checkpoint + WAL
+
+```bash
+# Restore from snapshot
+./build/baradadb --recover \
+  --checkpoint=/backup/snapshot.db \
+  --wal-dir=/backup/wal
+
+# Recovery to specific LSN
+./build/baradadb --recover \
+  --checkpoint=/backup/snapshot.db \
+  --wal-dir=/backup/wal \
+  --target-lsn=15420
+
+# Recovery to specific time
+./build/baradadb --recover \
+  --checkpoint=/backup/snapshot.db \
+  --wal-dir=/backup/wal \
+  --target-time="2025-01-15T10:30:00Z"
+```
+
+### Incremental Backups
+
+Incremental backups only copy changed SSTables:
+
+```bash
+./build/baradadb --backup-incremental \
+  --last-backup=/backup/previous \
+  --output=/backup/incremental_$(date +%Y%m%d)
+```
+
+## Replication as Backup
+
+For continuous protection, use streaming replication:
+
+### Primary
+
+```bash
+BARADB_REPLICATION_ENABLED=true \
+BARADB_REPLICATION_MODE=async \
+./build/baradadb
+```
+
+### Replica
+
+```bash
+BARADB_REPLICATION_ENABLED=true \
+BARADB_REPLICATION_PRIMARY=primary:5432 \
+./build/baradadb
+```
+
+## Disaster Recovery
+
+### Recovery Procedures
+
+#### Scenario 1: Single File Corruption
+
+```bash
+# Identify corrupted SSTable from logs
+# Restore specific SSTable from backup
+cp /backup/sstables/000012.sst ./data/sstables/
+
+# Rebuild index
+./build/baradadb --rebuild-index
+```
+
+#### Scenario 2: Complete Data Loss
+
+```bash
+# 1. Restore latest snapshot
+cp /backup/snapshot.db ./data/
+
+# 2. Replay WAL
+./build/baradadb --recover --wal-dir=/backup/wal
+
+# 3. Verify
+curl http://localhost:8080/health
+```
+
+#### Scenario 3: Cluster Node Failure
+
+```bash
+# For Raft clusters, simply start a new node
+BARADB_RAFT_NODE_ID=newnode \
+BARADB_RAFT_PEERS=node1:9001,node2:9001 \
+./build/baradadb
+
+# The new node will catch up via Raft log replication
+```
+
+## Backup Verification
+
+Always verify backups:
+
+```bash
+# Restore to temporary directory
+./build/baradadb --recover \
+  --checkpoint=/backup/snapshot.db \
+  --data-dir=/tmp/verify_data
+
+# Run consistency check
+curl http://localhost:8080/api/admin/check
+```
+
+## Storage Requirements
+
+| Backup Type | Size | Frequency | Retention |
+|-------------|------|-----------|-----------|
+| Full snapshot | ~1× data size | Daily | 7 days |
+| Incremental | ~0.1× data size | Hourly | 24 hours |
+| WAL archive | ~0.05× data size / day | Continuous | 30 days |
+
+## Best Practices
+
+1. **Test restores regularly** — A backup you can't restore is useless
+2. **Store backups offsite** — Use S3, GCS, or Azure Blob
+3. **Encrypt backups** — Use `gpg` or OS-level encryption
+4. **Monitor backup jobs** — Alert on failed backups
+5. **Document RTO/RPO** — Know your recovery time and point objectives
+
+### Cloud Backup Upload
+
+```bash
+# Upload to S3
+aws s3 cp /backup/snapshot.db s3://my-bucket/baradb/
+
+# Upload to GCS
+gsutil cp /backup/snapshot.db gs://my-bucket/baradb/
+
+# Upload to Azure
+az storage blob upload \
+  --container-name backups \
+  --file /backup/snapshot.db \
+  --name baradb/snapshot.db
+```