Preview tab crashes with 'Fetcher' object has no attribute `'raw_content'`

**Describe the bug**
The "Preview" tab throws an error for a PDF watch when an "Extract text" regex filter is applied:

`Error: 'Fetcher' object has no attribute 'raw_content'`

The underlying check/diff mechanism (recheck + history/diff view) works correctly and shows the filtered text as expected — only the Preview tab itself crashes.

**Version**
v0.60.3

**How did you install?**
Docker

**To Reproduce**

Steps to reproduce the behavior:
1. Add a PDF watch, e.g.: `https://www.bundesnetzagentur.de/DE/Fachthemen/Telekommunikation/Frequenzen/SpezielleAnwendungen/Amateurfunk/_DL/Pruefungstermine.pdf`
2. Go to "Filters & Triggers" and add an Extract text regex, e.g.:
`/Eschborn.*?(?=Göttingen)/s`
3. Save the watch
4. Open the "Preview" tab
5. Error is shown instead of the extracted text

! ALWAYS INCLUDE AN EXAMPLE URL WHERE IT IS POSSIBLE TO RE-CREATE THE ISSUE - USE THE 'SHARE WATCH' FEATURE AND PASTE IN THE SHARE-LINK!
https://changedetection.io/share/YziX8OuOE1ka - I guess this one won't work, as it is a local installation. When I try to access it, I get an error message myself.

**Expected behavior**
Preview tab should show the extracted/filtered text, same as what the diff/history view already shows correctly.

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
- OS: Windows 11
- Browser: Chrome
- Version: 152.0.7977.77

**Additional context**
Traceback from Dockhand's logs for my ChangeDetection container:
```
2026-09-08T16:24:07.444Z [ChangeDetection] 2026-09-08 18:24:07.443 | DEBUG | changedetectionio.model.Watch:history:471 - Reading watch history index for 67bab8dc-44d5-40aa-8e15-d89ef9b62417
2026-09-08T16:24:07.446Z [ChangeDetection] 2026-09-08 18:24:07.446 | DEBUG | changedetectionio.model.Watch:history:471 - Reading watch history index for 67bab8dc-44d5-40aa-8e15-d89ef9b62417
2026-09-08T16:24:07.449Z [ChangeDetection] 2026-09-08 18:24:07.448 | WARNING | changedetectionio.processors.magic:__init__:91 - Error getting a more precise mime type from 'puremagic' library (Could not identify file), using content-based detection
2026-09-08T16:24:07.449Z [ChangeDetection] 2026-09-08 18:24:07.449 | WARNING | changedetectionio.processors.magic:__init__:91 - Error getting a more precise mime type from 'puremagic' library (Could not identify file), using content-based detection
2026-09-08T16:24:07.449Z [ChangeDetection] 2026-09-08 18:24:07.449 | WARNING | changedetectionio.processors.magic:__init__:91 - Error getting a more precise mime type from 'puremagic' library (Could not identify file), using content-based detection
2026-09-08T16:24:07.451Z [ChangeDetection] 172.22.0.1 - - [08/Sep/2026 18:24:07] "POST /edit/67bab8dc-44d5-40aa-8e15-d89ef9b62417/preview-rendered HTTP/1.1" 200 -
```

Thank you and let me know in case you need more/different/other data or info from me.