URL with Jinja2 variables not resolved/clickable on diff page

**Describe the bug**
When a watched URL contains Jinja2 variables (e.g., `{% now 'utc', '%Y' %}`), the URL displayed at the top of the `/diff` page shows the raw unparsed Jinja2 template string instead of the resolved URL. This makes the link non-functional/not clickable.

**Version**
v0.52.7

**How did you install?**
Proxmox LXC using community scripts

**To Reproduce**
1. Create a watch with a URL containing Jinja2: `https://github.com/python-organizers/conferences/raw/refs/heads/main/{% now 'utc', '%Y' %}.csv`
2. Wait for a change to be detected
3. Click "History" or the change notification to view the diff
4. Observe the URL at the top shows `{% now 'utc', '%Y' %}` instead of `2026`

**Expected behavior**
The URL displayed on the `/diff` page should show the resolved URL (`https://github.com/python-organizers/conferences/raw/refs/heads/main/2026.csv`) and be clickable.

**Screenshots**

**Desktop**
- OS: Windows
- Browser: Firefox

**Additional context**
The fetch itself works correctly (Jinja2 is evaluated when making the request), but the display/link on the diff page uses the raw template string.