feat: Phase 6 — Docker + docker-compose + backup/restore CLI

- Dockerfile: multi-stage build (nim:alpine -> alpine), env-configurable
- docker-compose.yml: single node with volume + healthcheck
- backup.nim: backup/restore tar.gz snapshots, list/cleanup
- CLI: baradadb backup|restore|list --data-dir=DIR
- All 216 tests pass

Dockerfile

@@ -0,0 +1,18 @@
+FROM nim:2.2-alpine AS builder
+WORKDIR /build
+COPY baradadb.nimble .
+COPY src/ src/
+RUN nimble install -d -y || true
+RUN nim c -d:release --opt:speed -o:baradadb src/baradadb.nim
+
+FROM alpine:latest
+WORKDIR /app
+COPY --from=builder /build/baradadb .
+RUN mkdir -p /data
+ENV BARADB_PORT=9000
+ENV BARADB_DATA_DIR=/data
+ENV BARADB_HTTP_PORT=8080
+ENV BARADB_WS_PORT=8081
+EXPOSE 9000 8080 8081
+VOLUME ["/data"]
+CMD ["./baradadb"]

docker-compose.yml

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+version: "3.9"
+services:
+  baradb:
+    build: .
+    ports:
+      - "9000:9000"
+      - "8080:8080"
+      - "8081:8081"
+    volumes:
+      - baradb_data:/data
+    environment:
+      - BARADB_PORT=9000
+      - BARADB_DATA_DIR=/data
+      - BARADB_HTTP_PORT=8080
+      - BARADB_WS_PORT=8081
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
+      interval: 10s
+      timeout: 5s
+      retries: 3
+
+volumes:
+  baradb_data:

src/barabadb/core/backup.nim

@@ -0,0 +1,102 @@
+## BaraDB Backup & Restore — tar.gz snapshots
+import std/os
+import std/osproc
+import std/strutils
+import std/times
+
+type
+  Backup* = object
+    path*: string
+    timestamp*: int64
+    size*: int64
+
+proc backupDataDir*(dataDir: string, output: string): bool =
+  ## Create a tar.gz backup of the data directory
+  if not dirExists(dataDir):
+    echo "Data directory not found: ", dataDir
+    return false
+
+  let parent = parentDir(dataDir)
+  let name = lastPathPart(dataDir)
+  let cmd = "tar -czf " & quoteShell(output) & " -C " & quoteShell(parent) & " " & quoteShell(name)
+  let exitCode = execCmd(cmd)
+  return exitCode == 0
+
+proc restoreDataDir*(input: string, dataDir: string): bool =
+  ## Restore from a tar.gz backup
+  if not fileExists(input):
+    echo "Backup file not found: ", input
+    return false
+
+  if dirExists(dataDir):
+    removeDir(dataDir)
+  createDir(dataDir)
+
+  let cmd = "tar -xzf " & quoteShell(input) & " -C " & quoteShell(dataDir)
+  let exitCode = execCmd(cmd)
+  return exitCode == 0
+
+proc listBackups*(dataDir: string): seq[Backup] =
+  result = @[]
+  for kind, path in walkDir(parentDir(dataDir)):
+    let (_, name, ext) = splitFile(path)
+    if ext == ".gz":
+      var backup = Backup(path: path)
+      backup.size = getFileSize(path)
+      result.add(backup)
+
+proc cleanupOldBackups*(dataDir: string, keepLast: int = 5) =
+  var backups = listBackups(dataDir)
+  if backups.len <= keepLast:
+    return
+  for i in 0..<(backups.len - keepLast):
+    removeFile(backups[i].path)
+
+when isMainModule:
+  import std/os
+  import std/parseopt
+
+  var
+    command = ""
+    dataDir = "data/server"
+    target = ""
+
+  for kind, key, val in getopt():
+    case kind
+    of cmdArgument:
+      if command == "":
+        command = key
+      elif target == "":
+        target = key
+    of cmdLongOption, cmdShortOption:
+      case key
+      of "data-dir", "d": dataDir = val
+      of "output", "o": target = val
+      of "input", "i": target = val
+      else: discard
+    of cmdEnd: discard
+
+  case command
+  of "backup":
+    let outputFile = if target.len > 0: target else: "backup_" & $getTime().toUnix() & ".tar.gz"
+    let ok = backupDataDir(dataDir, outputFile)
+    if ok:
+      echo "Backup created: ", outputFile
+    else:
+      quit("Backup failed", 1)
+  of "restore":
+    if target.len == 0:
+      quit("Usage: backup restore --input=<file.tar.gz>", 1)
+    let ok = restoreDataDir(target, dataDir)
+    if ok:
+      echo "Restored from: ", target
+    else:
+      quit("Restore failed", 1)
+  of "list":
+    let backups = listBackups(dataDir)
+    echo "Backups:"
+    for b in backups:
+      echo "  ", b.path, " (", b.size, " bytes)"
+  else:
+    echo "Usage: backup <backup|restore|list> [--data-dir=DIR] [--output/-i=FILE]"
+    quit(1)