feat(ads/seo/release): v1.2.0 with live Google Ads, isolated ad profile, ads.txt, and SEO/AEO/GEO optimization

src/Paca.Core/AudioDynamicRangeCompressor.cs

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+using System;
+using System.Globalization;
+
+namespace Paca.Core;
+
+/// <summary>
+/// Predefined dynamic range compression presets for dialogue clarity and evening listening.
+/// </summary>
+public enum CompressorPreset
+{
+    None,
+    NightListening,
+    PodcastSpeech,
+    BroadcastStandard
+}
+
+/// <summary>
+/// Intelligent audio dynamic range compression (DRC) and peak limiter filter generator.
+/// Balances quiet speech and loud sound effects (gunfire, explosions) for clear, non-fatiguing audio.
+/// </summary>
+public static class AudioDynamicRangeCompressor
+{
+    /// <summary>
+    /// Builds the ffmpeg acompressor and alimiter filter chain for the given preset.
+    /// </summary>
+    public static string BuildFilter(CompressorPreset preset)
+    {
+        return preset switch
+        {
+            CompressorPreset.NightListening => "acompressor=threshold=-24dB:ratio=6:attack=5:release=100:makeup=6dB,alimiter=limit=-1dB",
+            CompressorPreset.PodcastSpeech => "acompressor=threshold=-20dB:ratio=4:attack=10:release=150:makeup=4dB,alimiter=limit=-1dB",
+            CompressorPreset.BroadcastStandard => "acompressor=threshold=-18dB:ratio=8:attack=2:release=80:makeup=8dB,alimiter=limit=0dB",
+            _ => "anull"
+        };
+    }
+
+    /// <summary>
+    /// Builds custom compressor filter chain with granular acoustic parameters.
+    /// </summary>
+    public static string BuildCustomFilter(double thresholdDb, double ratio, double attackMs, double releaseMs, double makeupDb, double limitPeakDb)
+    {
+        var inv = CultureInfo.InvariantCulture;
+        return $"acompressor=threshold={thresholdDb.ToString("0.##", inv)}dB:ratio={ratio.ToString("0.##", inv)}:attack={attackMs.ToString("0.##", inv)}:release={releaseMs.ToString("0.##", inv)}:makeup={makeupDb.ToString("0.##", inv)}dB,alimiter=limit={limitPeakDb.ToString("0.##", inv)}dB";
+    }
+
+    /// <summary>
+    /// Builds full ffmpeg command line arguments for applying DRC to video or audio files.
+    /// </summary>
+    public static string BuildFfmpegArgs(string inputPath, string outputPath, CompressorPreset preset, bool copyVideo = true, int audioBitrateKbps = 192)
+    {
+        string vCodec = copyVideo ? "-c:v copy" : "-c:v libx264 -crf 20 -preset fast";
+        var filter = BuildFilter(preset);
+        return $"-hide_banner -y -i \"{inputPath}\" {vCodec} -af \"{filter}\" -c:a aac -b:a {audioBitrateKbps}k \"{outputPath}\"";
+    }
+}