Summary

• Add etcd v3 driver plugin (registry-distributed) using HTTP/JSON gateway, no C bridge needed
• Prefix-tree key browsing: sidebar shows key prefixes as directories (/app/, /users/, (root))
• etcdctl-compatible editor: get, put, del, watch, lease, member, endpoint, auth, user, role commands with flags
• Full mTLS support (CA cert + client cert + client key), username/password auth with token management
• Lease management (grant, revoke, timetolive, list), bounded watch, cluster info
• CRUD via data grid: edit values, rename keys, attach leases, delete keys
• Fix QueryTab.buildBaseTableQuery to use plugin's buildBrowseQuery when available, so NoSQL plugins get table-specific initial queries instead of hardcoded SCAN commands
• Fix DispatchQueue.sync missing execute: label in SSH tunnel code

Closes #339

Test plan

• Start local etcd: docker run -d --name etcd -p 2379:2379 -e ALLOW_NONE_AUTHENTICATION=yes quay.io/coreos/etcd:v3.5.0 /usr/local/bin/etcd --advertise-client-urls http://0.0.0.0:2379 --listen-client-urls http://0.0.0.0:2379
• Seed test data: etcdctl --endpoints=http://127.0.0.1:2379 put /app/config/db_host localhost (and more keys)
• Connect in TablePro: host 127.0.0.1, port 2379, no auth, TLS disabled
• Verify sidebar shows prefix groups (/app/, /users/, (root))
• Click sidebar items and verify table-specific key data loads
• Test editor commands: get /app/config/db_host, member list, endpoint status, lease list
• Test CRUD: edit a value, add a key, delete a key via data grid
• Verify existing Redis plugin still works correctly (regression)

Summary by CodeRabbit

• New Features

  • Adds a full etcd v3 plugin: browse, query-builder integration, edit key/value data, lease management, watch streams, auth/user/role management, cluster/endpoint info, compaction, and etcdctl-style command support. Etcd is selectable as a database type with TLS/mTLS connection options and command completions.

• Tests

  • Extensive unit tests for command parsing, query building, HTTP utilities, and statement generation.

• Chores

  • Project integration and plugin packaging entries added.

• Documentation

  • Changelog updated with etcd v3 plugin entry.