chore: reduce log volume on server startup (#16608)

Addresses https://github.com/coder/coder/issues/16231.

This PR reduces the volume of logs we print after server startup in
order to surface the web UI URL better.

Here are the logs after the changes a couple of seconds after starting
the server:

<img width="868" alt="Screenshot 2025-02-18 at 16 31 32"
src="https://github.com/user-attachments/assets/786dc4b8-7383-48c8-a5c3-a997c01ca915"
/>

The warning is due to running a development site-less build. It wouldn't
show in a release build.

tailnet/controllers.go

@@ -1370,7 +1370,7 @@ func (c *Controller) Run(ctx context.Context) {
 				c.logger.Error(c.ctx, "failed to dial tailnet v2+ API", errF)
 				continue
 			}
-			c.logger.Info(c.ctx, "obtained tailnet API v2+ client")
+			c.logger.Debug(c.ctx, "obtained tailnet API v2+ client")
 			err = c.precheckClientsAndControllers(tailnetClients)
 			if err != nil {
 				c.logger.Critical(c.ctx, "failed precheck", slog.Error(err))
@@ -1379,7 +1379,7 @@ func (c *Controller) Run(ctx context.Context) {
 			}
 			retrier.Reset()
 			c.runControllersOnce(tailnetClients)
-			c.logger.Info(c.ctx, "tailnet API v2+ connection lost")
+			c.logger.Debug(c.ctx, "tailnet API v2+ connection lost")
 		}
 	}()
 }