fix: DM close visibility flag, wire Remove Friend button, harden deploy script

- Redesign DM close as a visibility flag (closed column) instead of row deletion,
  so message broadcasts still reach users who closed a DM conversation
- Add broadcastDmMessage() helper that auto-resurfaces closed DMs when new messages arrive
- Wire Remove Friend button in DM welcome header with onClick handler and friend check
- Fix deploy.sh to cd to its own directory so rsync always runs from project root

packages/server/src/db/schema.ts

@@ -74,6 +74,7 @@ export const dmChannels = sqliteTable('dm_channels', {
 export const dmMembers = sqliteTable('dm_members', {
   dmChannelId: text('dm_channel_id').notNull().references(() => dmChannels.id, { onDelete: 'cascade' }),
   userId: text('user_id').notNull().references(() => users.id, { onDelete: 'cascade' }),
+  closed: integer('closed').default(0),
 }, (table) => ({
   pk: primaryKey({ columns: [table.dmChannelId, table.userId] }),
 }));