v0.0.20: file transfer in groups

/file <path> now works in group mode (#group):
- Sends file header + chunks to each group member
- Same fan-out approach as group text messages
- Each member receives and reassembles independently
- Progress shown: "Sending 'file.pdf' to group #ops..."

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/Cargo.lock

@@ -2789,7 +2789,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-client"
-version = "0.0.18"
+version = "0.0.19"
 dependencies = [
  "anyhow",
  "argon2",
@@ -2822,7 +2822,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-mule"
-version = "0.0.18"
+version = "0.0.19"
 dependencies = [
  "anyhow",
  "clap",
@@ -2831,7 +2831,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-protocol"
-version = "0.0.18"
+version = "0.0.19"
 dependencies = [
  "base64",
  "bincode",
@@ -2856,7 +2856,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-server"
-version = "0.0.18"
+version = "0.0.19"
 dependencies = [
  "anyhow",
  "axum",
@@ -2883,7 +2883,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-wasm"
-version = "0.0.18"
+version = "0.0.19"
 dependencies = [
  "base64",
  "bincode",