…ests; stabilize AttemptCounter timing (#4822)

# Description of Changes

- **What was changed**
  - Added new MVC tests:
- `ConverterWebControllerTest` covering simple converter routes,
`/pdf-to-cbr` enable/disable behavior via `EndpointConfiguration`,
Python availability flag, and `maxDPI` defaults/overrides for
`/pdf-to-img` and `/pdf-to-video`.
- `GeneralWebControllerTest` covering many editor/organizer routes’
view/model mapping, `/sign` font discovery from classpath and
`/opt/static/fonts`, handling of missing `UserService`, robust filtering
of malformed font entries, and `/pipeline` JSON config discovery with
graceful fallback on `Files.walk` errors.
- `HomeWebControllerTest` covering `/about`, `/releases`, legacy
redirects, root page’s `SHOW_SURVEY` behavior, `/robots.txt` for
`googlevisibility` true/false/null, and `/licenses` JSON parsing with
IOException fallback.
  - Extended proprietary security tests:
- `LoginAttemptServiceTest` (reflective construction) validating
`getRemainingAttempts(...)` for disabled/blank keys, empty cache,
decreasing logic, and intentionally negative values when over the limit
(documented current behavior).
  - Hardened `AttemptCounterTest`:
- Eliminated timing flakiness by using generous windows and setting
`lastAttemptTime` to “now”.
- Added edge-case assertions for zero/negative windows to document
current semantics after switching comparison to `elapsed >=
attemptIncrementTime`.
- **Why the change was made**
- To increase test coverage across critical web endpoints and security
logic, document current edge-case behavior, and prevent regressions
around view resolution, environment/property-driven flags, resource
discovery, and timing-sensitive logic.


---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.