perf(scanner-effect): Optimize fake-scanner effect with multithreading (#4614)

# Description of Changes

TLDR: should be 3-4x faster by my (very) unscientific benchmarks (I ran
the new and old with 5 docs and averaged out the results)


Notes:
- Made Threadpool and pages are rendered separately (large perf
improvement over previous code)
- Most of actual rendering/processing logic remain unchanged
- DPI values are now more "reasonable
- Buffering related perf gains also somewhat significant


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---

## 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)
- [x] 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)

### 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)

- [x] 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.

---------

Signed-off-by: Balázs Szücs <bszucs1209@gmail.com>

app/core/src/main/java/stirling/software/SPDF/model/api/misc/ScannerEffectRequest.java

@@ -79,14 +79,6 @@ public class ScannerEffectRequest {
     @Schema(description = "Whether advanced settings are enabled", example = "false")
     private boolean advancedEnabled = false;
 
-    public int getQualityValue() {
-        return switch (quality) {
-            case low -> 30;
-            case medium -> 60;
-            case high -> 100;
-        };
-    }
-
     public int getRotationValue() {
         return switch (rotation) {
             case none -> 0;
@@ -97,26 +89,26 @@ public class ScannerEffectRequest {
     }
 
     public void applyHighQualityPreset() {
-        this.blur = 0.1f;
+        this.blur = 0.10f;
         this.noise = 1.0f;
-        this.brightness = 1.02f;
-        this.contrast = 1.05f;
-        this.resolution = 300;
+        this.brightness = 1.03f;
+        this.contrast = 1.06f;
+        this.resolution = 150;
     }
 
     public void applyMediumQualityPreset() {
-        this.blur = 0.5f;
-        this.noise = 3.0f;
-        this.brightness = 1.05f;
-        this.contrast = 1.1f;
-        this.resolution = 300;
+        this.blur = 0.10f;
+        this.noise = 1.0f;
+        this.brightness = 1.06f;
+        this.contrast = 1.12f;
+        this.resolution = 100;
     }
 
     public void applyLowQualityPreset() {
-        this.blur = 1.0f;
-        this.noise = 5.0f;
-        this.brightness = 1.1f;
-        this.contrast = 1.2f;
-        this.resolution = 150;
+        this.blur = 0.9f;
+        this.noise = 2.5f;
+        this.brightness = 1.08f;
+        this.contrast = 1.15f;
+        this.resolution = 75;
     }
 }