Implement E2EE and message content moderation

apps/supabase/migrations/20260103000000_add_message_deletion.sql

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+-- Add deleted_at column to messages table for "delete for everyone"
+ALTER TABLE messages ADD COLUMN deleted_at TIMESTAMPTZ;
+
+-- Create message_deletions table for "delete for self" (per-user deletions)
+CREATE TABLE message_deletions (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  message_id UUID NOT NULL REFERENCES messages(id) ON DELETE CASCADE,
+  user_id UUID NOT NULL REFERENCES auth.users(id) ON DELETE CASCADE,
+  deleted_at TIMESTAMPTZ DEFAULT now(),
+  UNIQUE(message_id, user_id)
+);
+
+-- Index for efficient lookup when filtering messages
+CREATE INDEX idx_message_deletions_user_message ON message_deletions(user_id, message_id);
+CREATE INDEX idx_messages_deleted_at ON messages(deleted_at) WHERE deleted_at IS NOT NULL;
+
+-- Enable RLS on message_deletions
+ALTER TABLE message_deletions ENABLE ROW LEVEL SECURITY;
+
+-- RLS Policies for message_deletions
+
+-- Users can view their own deletions (needed for filtering)
+CREATE POLICY "Users can view own deletions"
+  ON message_deletions FOR SELECT
+  USING (user_id = auth.uid());
+
+-- Users can insert their own deletions (for messages in their matches)
+CREATE POLICY "Users can delete messages for self"
+  ON message_deletions FOR INSERT
+  WITH CHECK (
+    user_id = auth.uid() AND
+    EXISTS (
+      SELECT 1 FROM messages m
+      JOIN matches ma ON ma.id = m.match_id
+      JOIN profiles p ON p.couple_id = ma.couple_id
+      WHERE m.id = message_deletions.message_id
+      AND p.id = auth.uid()
+    )
+  );
+
+-- Update messages RLS policy to allow authors to set deleted_at
+CREATE POLICY "Authors can soft delete messages for everyone"
+  ON messages FOR UPDATE
+  USING (user_id = auth.uid())
+  WITH CHECK (user_id = auth.uid());
+
+-- Add to realtime for live updates
+ALTER PUBLICATION supabase_realtime ADD TABLE message_deletions;
+
+-- Comments for documentation
+COMMENT ON COLUMN messages.deleted_at IS 'Timestamp when message was deleted for everyone (author-only action). Shows "Message deleted" to all users.';
+COMMENT ON TABLE message_deletions IS 'Per-user message deletions for "delete for self" functionality. Message still visible to other user.';