feat: extend workspace build reasons to track connection types (#18827)

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
(https://github.com/coder/vscode-coder/pull/550)
- JetBrains connections: Will be set to `jetbrains_connection` by the
Jetbrains Toolbox
(https://github.com/coder/coder-jetbrains-toolbox/pull/150) and
Jetbrains Gateway extension
(https://github.com/coder/jetbrains-coder/pull/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"
/>

coderd/database/migrations/000350_extend_workspace_build_reason.down.sql

@@ -0,0 +1 @@
+-- It's not possible to delete enum values.

coderd/database/migrations/000350_extend_workspace_build_reason.up.sql

@@ -0,0 +1,5 @@
+ALTER TYPE build_reason ADD VALUE IF NOT EXISTS 'dashboard';
+ALTER TYPE build_reason ADD VALUE IF NOT EXISTS 'cli';
+ALTER TYPE build_reason ADD VALUE IF NOT EXISTS 'ssh_connection';
+ALTER TYPE build_reason ADD VALUE IF NOT EXISTS 'vscode_connection';
+ALTER TYPE build_reason ADD VALUE IF NOT EXISTS 'jetbrains_connection';