chore: migrate from bincode to postcard serialization

- Replace bincode with postcard in workspace dependencies
- Update all bincode::serialize() calls to postcard::to_stdvec()
- Update all bincode::deserialize() calls to postcard::from_bytes()
- Bump version from 0.8.2 to 0.8.3
- Updated files:
  - Cargo.toml: workspace dependency change
  - communitas-core/Cargo.toml: dependency + version constraint
  - communitas-headless/Cargo.toml: version constraint
  - communitas-mcp/Cargo.toml: version constraint
  - gossip/context.rs: backup encryption/decryption
  - gossip/boot.rs: CRDT delta serialization
  - gossip/sites.rs: site protocol requests/responses
  - gossip/backup.rs: backup data encryption
  - gossip/sites_listener.rs: wire protocol handling
  - gossip/sites_dispatcher.rs: message routing
  - storage/local_storage.rs: shard serialization (commented code)
  - presence_service.rs: beacon encryption
  - doc_replicator.rs: encrypted document storage
  - tests/sites_integration_test.rs: test serialization

Postcard provides deterministic, zero-copy serialization with
better performance characteristics than bincode.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: dirvine

Cargo.lock

@@ -13,7 +13,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.8.2"
+version = "0.8.3"
 edition = "2024"
 authors = ["David Irvine <[email protected]>", "Saorsa Labs"]
 license = "GPL-3.0"
@@ -62,7 +62,7 @@ tower-http = { version = "0.5", features = ["cors", "trace"] }
 # Serialization
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-bincode = "1.3"
+postcard = { version = "1.1", features = ["use-std"] }
 toml = "0.8"
 
 # Error handling

Cargo.toml

@@ -57,7 +57,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 ciborium = "0.2"  # Replace deprecated serde_cbor
 serde_bytes = "0.11"
-bincode = "1.3"
+postcard = { version = "1.1", features = ["use-std"] }
 toml = "0.8"
 bytes = "1.5"
 
@@ -119,7 +119,7 @@ reed-solomon-erasure = "6.0.0"
 mime_guess = "2.0"
 
 # Local dependencies (version required for crates.io publishing)
-communitas-kanban = { version = "=0.8.2", path = "../communitas-kanban" }
+communitas-kanban = { version = "=0.8.3", path = "../communitas-kanban" }
 
 [features]
 default = []

communitas-core/Cargo.toml

@@ -474,7 +474,7 @@ impl DocReplicator {
         };
 
         let blob =
-            bincode::serialize(encrypted).map_err(|e| anyhow!("Serialization failed: {}", e))?;
+            postcard::to_stdvec(encrypted).map_err(|e| anyhow!("Serialization failed: {}", e))?;
 
         Ok(Some(blob))
     }

communitas-core/src/doc_replicator.rs

@@ -100,7 +100,7 @@ impl BackupManager {
     /// Package format: [nonce (12 bytes) || ciphertext || key (32 bytes)]
     pub async fn encrypt_backup(&self, backup: &BackupData, _recipient: &str) -> Result<Vec<u8>> {
         // 1. Serialize backup data
-        let plaintext = bincode::serialize(backup).context("Failed to serialize backup data")?;
+        let plaintext = postcard::to_stdvec(backup).context("Failed to serialize backup data")?;
 
         // 2. Generate per-backup encryption key (ChaCha20Poly1305)
         let key = SymmetricKey::generate();
@@ -155,7 +155,7 @@ impl BackupManager {
 
         // 5. Deserialize backup data
         let backup: BackupData =
-            bincode::deserialize(&plaintext).context("Failed to deserialize backup data")?;
+            postcard::from_bytes(&plaintext).context("Failed to deserialize backup data")?;
 
         Ok(backup)
     }