🐛 Fixed post analytics missing first-day traffic on later days (#28233)

ref https://linear.app/ghost/issue/ONC-1771

Post analytics was calculating the publish-date range from elapsed
hours, while the chart query dates are calendar-day based. This meant
posts could lose their publication-day traffic whenever the current time
was earlier than the original publish time.

So if you published on Monday at 11am, you'd have the following:
- Monday: you'd see stats all day
- Tuesday before 11am: you'd only see Tuesday stats
- Tuesday after 11am: you'd correctly see Tuesday and Monday
and so on

This PR updates the range calculation to count inclusive calendar days
in the same timezone used by the chart date query, so the publish day is
always included.

<h3>Before</h3>
  <table>
    <tr>
      <th>Analytics overview</th>
      <th>Post analytics</th>
    </tr>
    <tr>
      <td>Shows <strong>115 views</strong> for the post.</td>
<td>Shows only <strong>15 unique visitors</strong>: 10 on 5/27 and 5 on
5/28. The <strong>100 visitors from publish day, 5/26, are
missing</strong>.</td>
    </tr>
    <tr>
      <td>
<img width="1270" height="936" alt="Screenshot 2026-05-28 at 12 28 16
PM"
src="https://github.com/user-attachments/assets/af7ff895-62d5-4818-bf8c-cd7d0744f12c"
/> </td>
      <td>
<img width="1280" height="682" alt="Screenshot 2026-05-28 at 12 28 05
PM"
src="https://github.com/user-attachments/assets/a0848cad-a630-475f-9071-4d2f0c5ae373"
/> </td>
    </tr>
  </table>

<table>
 <tr>
<td>The control renders properly, however. See analytics overview above:
we expect 90, we get 90 on post analytics</td>
</tr>
  <tr>
    <td>
<img width="1280" height="682" alt="Screenshot 2026-05-28 at 12 28
05 PM"
src="https://github.com/user-attachments/assets/a6273b72-8752-4380-b208-366a150d1fb2"
/> </td>
  </tr>
<table>

  <h3>After</h3>

  <table>
    <tr>
      <th>Post analytics</th>
    </tr>
    <tr>
<td>Correctly shows data for all 3 days, including publish day.</td>
    </tr>
    <tr>
      <td>
<img width="1292" height="812" alt="Screenshot 2026-05-28 at 12 32 02
PM"
src="https://github.com/user-attachments/assets/896e0070-e35a-4265-bca6-657901d8d0c7"
/> </td>
    </tr>
  </table>