docs: add web dashboard documentation (#8864)

- New docs page: user-guide/features/web-dashboard.md covering
  quick start, prerequisites, all three pages (Status, Config, API Keys),
  the /reload slash command, REST API endpoints, CORS config, and
  development workflow
- Added 'Management' category in sidebar for web-dashboard
- Added 'hermes web' to CLI commands reference with options table
- Added '/reload' to slash commands reference (both CLI and gateway tables)

website/docs/reference/slash-commands.md

@@ -63,6 +63,7 @@ Type `/` in the CLI to open the autocomplete menu. Built-in commands are case-in
 | `/skills` | Search, install, inspect, or manage skills from online registries |
 | `/cron` | Manage scheduled tasks (list, add/create, edit, pause, resume, run, remove) |
 | `/reload-mcp` (alias: `/reload_mcp`) | Reload MCP servers from config.yaml |
+| `/reload` | Reload `.env` variables into the running session (picks up new API keys without restarting) |
 | `/plugins` | List installed plugins and their status |
 
 ### Info
@@ -133,6 +134,7 @@ The messaging gateway supports the following built-in commands inside Telegram,
 | `/background <prompt>` | Run a prompt in a separate background session. Results are delivered back to the same chat when the task finishes. See [Messaging Background Sessions](/docs/user-guide/messaging/#background-sessions). |
 | `/plan [request]` | Load the bundled `plan` skill to write a markdown plan instead of executing the work. Plans are saved under `.hermes/plans/` relative to the active workspace/backend working directory. |
 | `/reload-mcp` (alias: `/reload_mcp`) | Reload MCP servers from config. |
+| `/reload` | Reload `.env` variables into the running session. |
 | `/yolo` | Toggle YOLO mode — skip all dangerous command approval prompts. |
 | `/commands [page]` | Browse all commands and skills (paginated). |
 | `/approve [session\|always]` | Approve and execute a pending dangerous command. `session` approves for this session only; `always` adds to permanent allowlist. |