Increase H264/H265 bitrate multipliers to improve image quality

- H265: Increase base multiplier from 1.5x to 2.0x (33% more bitrate)
- H264: Increase base multiplier from 2.0x to 2.5x (25% more bitrate)
- Also adjusted high-bitrate decay factors proportionally
- At 1080p Balanced quality: H265 now uses ~2777 kbps (was 2084)
- Fixes issue where H265 had worse quality than VP8 software codec

Co-authored-by: rustdesk <71636191+rustdesk@users.noreply.github.com>

libs/scrap/src/common/hwcodec.rs

@@ -264,17 +264,21 @@ impl HwRamEncoder {
                 5.0
             }
         } else if h264 {
+            // Increased base multiplier from 2.0 to 2.5 to improve image quality
+            // while maintaining H264's compression efficiency
+            if base > threshold {
+                1.0 + 1.5 / (1.0 + (base - threshold) * decay_rate)
+            } else {
+                2.5
+            }
+        } else {
+            // H265: Increased base multiplier from 1.5 to 2.0 to fix poor image quality
+            // H265 should be more efficient than H264, but needs sufficient bitrate
             if base > threshold {
                 1.0 + 1.0 / (1.0 + (base - threshold) * decay_rate)
             } else {
                 2.0
             }
-        } else {
-            if base > threshold {
-                1.0 + 0.5 / (1.0 + (base - threshold) * decay_rate)
-            } else {
-                1.5
-            }
         };
         (base * factor) as u32
     }