feat: initial release with 48 Mattermost MCP tools

- 27 base tools: channels, messaging, users, reactions, files, DMs
- Team management: invite/remove users, get stats, list members
- Slash commands: execute /remind, /poll, etc.
- Webhook management: incoming and outgoing webhooks
- System tools: server config, logs, bulk status updates
- Channel admin: create, invite, leave, delete channels
- Read-only mode for safe exploration
- Dual token support (bot + PAT) for enhanced security
- Apache 2.0 licensed

CHANGELOG.md

@@ -0,0 +1,70 @@
+# Changelog
+
+All notable changes to the Mattermost MCP Server will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [1.0.0] - 2026-04-12
+
+### Added
+- Initial release of Mattermost MCP Server
+- Support for 22 MCP tools categorized as Read, Write, and Admin operations
+
+#### Read Operations (11)
+- `mattermost_list_channels` - List accessible channels in a team
+- `mattermost_get_channel_by_name` - Get a channel by name in a team
+- `mattermost_get_channel_info` - Get detailed channel information including member count
+- `mattermost_search_users` - Search for users by username, email, or display name
+- `mattermost_list_teams` - List all teams the bot has access to
+- `mattermost_search_posts` - Search for posts/messages in a team using search terms
+- `mattermost_get_thread` - Read all messages in a thread conversation
+- `mattermost_get_unread_count` - Get unread message counts for all channels in a team
+- `mattermost_mark_channel_read` - Mark a channel as read (clear unread notifications)
+- `mattermost_get_user_status` - Get the online status of a user (online, away, dnd, offline)
+- `mattermost_get_channel_messages` - Read message history from a channel
+
+#### Write Operations (8)
+- `mattermost_send_message` - Send a message to a channel or user
+- `mattermost_edit_message` - Edit an existing message
+- `mattermost_delete_message` - Delete a message from a channel
+- `mattermost_create_dm` - Create a direct message channel with a user
+- `mattermost_add_reaction` - Add an emoji reaction to a message
+- `mattermost_remove_reaction` - Remove an emoji reaction from a message
+- `mattermost_upload_file` - Upload a file to a channel or user
+- `mattermost_download_file` - Download a file from a message
+
+#### Admin Operations (4)
+- `mattermost_create_channel` - Create a new channel (public or private) in a team
+- `mattermost_invite_to_channel` - Invite a user to a channel
+- `mattermost_delete_channel` - Delete/archive a channel (soft delete by default)
+- `mattermost_leave_channel` - Remove self from a channel
+
+### Features
+- Multiple authentication methods (Bot tokens, PAT, User tokens)
+- Read-only mode for safe exploration (`--read-only` flag)
+- Debug logging support (`--debug` flag)
+- Configuration via environment variables or CLI flags
+- Comprehensive error handling with descriptive messages
+- File upload security with validation and restrictions
+- Integration tests for core functionality
+- OpenClaw and Claude Code configuration support
+
+### Security
+- Path traversal prevention for file operations
+- Dangerous file extension blocking
+- File size limits (50MB maximum)
+- MIME type whitelist validation for uploads
+- Token-safe logging (tokens are never logged)
+- TLS verification enabled by default
+- `--insecure` flag available only for development/testing
+
+## [Unreleased]
+
+### Planned
+- WebSocket support for real-time notifications
+- Additional search capabilities (file search, user directory)
+- Message threading improvements
+- Bulk operations support
+- Rate limiting and throttling options
+- Extended file type support for uploads