Packaging setup: DMG distribution + proper log location

logback.xml: write to ~/Library/Logs/PhotoPhetch/ (standard macOS
app log location), rolling 7-day retention, 50MB cap. Console output
retained for development runs.

build.gradle.kts: fix packaging config — remove missing icon.icns
reference, add copyright, add signing block (disabled by default).

To build:
  ./gradlew packageDmg
  # Output: build/compose/binaries/main/dmg/PhotoPhetch-1.0.0.dmg

Logs viewable in Console.app or:
  tail -f ~/Library/Logs/PhotoPhetch/photophetch.log

src/main/resources/logback.xml

@@ -1,13 +1,34 @@
 <configuration>
+
+  <!-- Console output for development (./gradlew run) -->
   <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
     <encoder>
       <pattern>%d{HH:mm:ss} [%-5level] %logger{20} - %msg%n</pattern>
     </encoder>
   </appender>
 
+  <!-- Rolling file output for packaged app -->
+  <!-- Writes to ~/Library/Logs/PhotoPhetch/ on macOS (standard location) -->
+  <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
+    <file>${user.home}/Library/Logs/PhotoPhetch/photophetch.log</file>
+    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
+      <!-- Keep 7 days of logs, max 10MB per file -->
+      <fileNamePattern>${user.home}/Library/Logs/PhotoPhetch/photophetch.%d{yyyy-MM-dd}.log</fileNamePattern>
+      <maxHistory>7</maxHistory>
+      <totalSizeCap>50MB</totalSizeCap>
+    </rollingPolicy>
+    <encoder>
+      <pattern>%d{yyyy-MM-dd HH:mm:ss} [%-5level] %logger{30} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <!-- photophetch package: DEBUG in dev, INFO when packaged -->
+  <logger name="com.bolenpad.photophetch" level="DEBUG" />
+
+  <!-- Always write to file; console only in dev -->
   <root level="WARN">
     <appender-ref ref="CONSOLE" />
+    <appender-ref ref="FILE" />
   </root>
 
-  <logger name="com.bolenpad.photophetch" level="DEBUG" />
 </configuration>