Phase 2: PostgreSQL, E2EE, channel CRUD, voice signaling, Slint migration

Server:
- PostgreSQL backend (Pool enum over Sqlite/PgPool, all storage methods dual-dialect)
- E2EE for DM (4 new protobuf packets, handlers, storage of ciphertext only)
- ChannelEdit packet + server-authoritative channel create/delete
- Gateway → voice-node membership signaling via broadcast channel

Client:
- E2EE crypto (X25519 from Ed25519, HKDF, ChaCha20-Poly1305) + UI lock icons
- E2EE net layer (PID 0x0071-0x0074, JSON payloads, dispatch, session handlers)
- Slint migration: all .slint files, bridge.rs, update.rs, main.rs rewritten
- Removed egui UI (~50 files) and all dead code (clean clippy -D warnings)

gateway/src/handler/dispatch.rs

@@ -11,7 +11,7 @@ use crate::{
     },
 };
 
-use super::{Ctx, channel, content, direct_message, friends, guild};
+use super::{Ctx, channel, content, direct_message, e2ee, friends, guild};
 
 pub async fn dispatch<S: AsyncRead + AsyncWrite + Unpin>(
     ctx: &mut Ctx<'_, S>,
@@ -43,6 +43,7 @@ pub async fn dispatch<S: AsyncRead + AsyncWrite + Unpin>(
                 &m.channel_id,
                 ctx.crypto,
                 ctx.state,
+                addr,
             )
             .await?;
         }
@@ -70,6 +71,12 @@ pub async fn dispatch<S: AsyncRead + AsyncWrite + Unpin>(
             )
             .await?;
         }
+        PacketId::ChannelEdit => {
+            channel::handle_channel_edit(
+                ctx.stream, ctx.seq, session_id, payload, ctx.crypto, ctx.state,
+            )
+            .await?;
+        }
         PacketId::ChannelList => {
             channel::handle_channel_list(ctx.stream, ctx.seq, session_id, ctx.crypto, ctx.state)
                 .await?;
@@ -275,6 +282,30 @@ pub async fn dispatch<S: AsyncRead + AsyncWrite + Unpin>(
             )
             .await?;
         }
+        PacketId::E2eeDmKeyExchange => {
+            e2ee::handle_e2ee_key_exchange(
+                ctx.stream, ctx.seq, session_id, payload, ctx.crypto, ctx.state,
+            )
+            .await?;
+        }
+        PacketId::E2eeDmKeyExchangeAck => {
+            e2ee::handle_e2ee_key_exchange_ack(
+                ctx.stream, ctx.seq, session_id, payload, ctx.crypto, ctx.state,
+            )
+            .await?;
+        }
+        PacketId::E2eeDmMessage => {
+            e2ee::handle_e2ee_dm_message(
+                ctx.stream, ctx.seq, session_id, payload, ctx.crypto, ctx.state,
+            )
+            .await?;
+        }
+        PacketId::E2eeDmHistory => {
+            e2ee::handle_e2ee_dm_history(
+                ctx.stream, ctx.seq, session_id, payload, ctx.crypto, ctx.state,
+            )
+            .await?;
+        }
         PacketId::Disconnect => debug!("{addr} DISCONNECT"),
         other => debug!("{addr} unhandled {:?}", other),
     }