feat: add fluxer upstream source and self-hosting documentation

- Clone of github.com/fluxerapp/fluxer (official upstream)
- SELF_HOSTING.md: full VM rebuild procedure, architecture overview,
  service reference, step-by-step setup, troubleshooting, seattle reference
- dev/.env.example: all env vars with secrets redacted and generation instructions
- dev/livekit.yaml: LiveKit config template with placeholder keys
- fluxer-seattle/: existing seattle deployment setup scripts

fluxer/fluxer_devops/cassandra/conf/jvm-server.options

@@ -0,0 +1,48 @@
+-Xms32G
+-Xmx32G
+-XX:+UseG1GC
+-XX:+ParallelRefProcEnabled
+-XX:MaxTenuringThreshold=2
+-XX:G1HeapRegionSize=16m
+-XX:G1RSetUpdatingPauseTimePercent=5
+-XX:MaxGCPauseMillis=300
+-XX:InitiatingHeapOccupancyPercent=70
+-Xlog:gc*,gc+age=trace,safepoint:file=/var/log/cassandra/gc.log:time,uptime,level,tags:filecount=10,filesize=100M
+-XX:+AlwaysPreTouch
+-XX:+IgnoreUnrecognizedVMOptions
+-Xss512k
+-XX:+UseTLAB
+-XX:+ResizeTLAB
+-XX:+PerfDisableSharedMem
+-XX:+UseStringDeduplication
+-XX:+HeapDumpOnOutOfMemoryError
+-XX:HeapDumpPath=/var/lib/cassandra/dumps
+-Djdk.attach.allowAttachSelf=true
+--add-exports=java.base/jdk.internal.misc=ALL-UNNAMED
+--add-exports=java.base/jdk.internal.ref=ALL-UNNAMED
+--add-exports=java.base/sun.nio.ch=ALL-UNNAMED
+--add-exports=java.management.rmi/com.sun.jmx.remote.internal.rmi=ALL-UNNAMED
+--add-exports=java.rmi/sun.rmi.registry=ALL-UNNAMED
+--add-exports=java.rmi/sun.rmi.server=ALL-UNNAMED
+--add-exports=java.sql/java.sql=ALL-UNNAMED
+--add-opens=java.base/java.lang.module=ALL-UNNAMED
+--add-opens=java.base/jdk.internal.loader=ALL-UNNAMED
+--add-opens=java.base/jdk.internal.ref=ALL-UNNAMED
+--add-opens=java.base/jdk.internal.reflect=ALL-UNNAMED
+--add-opens=java.base/jdk.internal.math=ALL-UNNAMED
+--add-opens=java.base/jdk.internal.module=ALL-UNNAMED
+--add-opens=java.base/jdk.internal.util.jar=ALL-UNNAMED
+--add-opens=jdk.management/com.sun.management.internal=ALL-UNNAMED
+-Dcom.sun.management.jmxremote.authenticate=false
+-Dcom.sun.management.jmxremote.ssl=false
+-Dcassandra.jmx.local.port=7199
+-Dcassandra.jmx.remote.port=7199
+-Djava.net.preferIPv4Stack=true
+-Dio.netty.tryReflectionSetAccessible=true
+-Dio.netty.allocator.useCacheForAllThreads=true
+-Dio.netty.eventLoop.maxPendingTasks=65536
+-Dcassandra.config=file:///etc/cassandra/cassandra.yaml
+-Dcassandra.logdir=/var/log/cassandra
+-Dcassandra.storagedir=/var/lib/cassandra
+-Djava.security.egd=file:/dev/urandom
+-Dfile.encoding=UTF-8