This PR introduces new build reason values to identify what type of
connection triggered a workspace build, helping to troubleshoot
workspace-related issues.

## Database Migration
Added migration 000349_extend_workspace_build_reason.up.sql that extends
the build_reason enum with new values:
```
dashboard, cli, ssh_connection, vscode_connection, jetbrains_connection
```

## Implementation
The build reason is specified through the API when creating new
workspace builds:

- Dashboard: Automatically sets reason to `dashboard` when users start
workspaces via the web interface
- CLI `start` command: Sets reason to `cli` when workspaces are started
via the command line
- CLI `ssh` command: Sets reason to ssh_connection when workspaces are
started due to SSH connections
- VS Code connections: Will be set to `vscode_connection` by the VS Code
extension through CLI hidden flag
(coder/vscode-coder#550)
- JetBrains connections: Will be set to `jetbrains_connection` by the
Jetbrains Toolbox
(coder/coder-jetbrains-toolbox#150) and
Jetbrains Gateway extension
(coder/jetbrains-coder#561)

## UI Changes:
* Tooltip with reason in Build history
<img width="309" height="457" alt="image"
src="https://github.com/user-attachments/assets/bde8440b-bf3b-49a1-a244-ed7e8eb9763c"
/>

* Reason in Audit Logs Row tooltip
<img width="906" height="237" alt="image"
src="https://github.com/user-attachments/assets/ebbb62c7-cf07-4398-afbf-323c83fb6426"
/>

<img width="909" height="188" alt="image"
src="https://github.com/user-attachments/assets/1ddbab07-44bf-4dee-8867-b4e2cd56ae96"
/>