set up for deployment

backend/scripts/004_add_public_sharing.sql

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+-- Migration: Add public sharing support via share tokens
+-- Dependencies: Run after 002_add_document_shares.sql
+-- Purpose: Add share_token and is_public columns used by share link feature
+
+-- Add columns for public sharing
+ALTER TABLE documents ADD COLUMN IF NOT EXISTS share_token VARCHAR(255);
+ALTER TABLE documents ADD COLUMN IF NOT EXISTS is_public BOOLEAN DEFAULT false NOT NULL;
+
+-- Create indexes for performance
+CREATE INDEX IF NOT EXISTS idx_documents_share_token ON documents(share_token) WHERE share_token IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_documents_is_public ON documents(is_public) WHERE is_public = true;
+
+-- Constraint: public documents must have a token
+-- This ensures data integrity - a document can't be public without a share token
+ALTER TABLE documents ADD CONSTRAINT check_public_has_token
+    CHECK (is_public = false OR (is_public = true AND share_token IS NOT NULL));
+
+-- Documentation
+COMMENT ON COLUMN documents.share_token IS 'Public share token for link-based access (base64-encoded random string, 32 bytes)';
+COMMENT ON COLUMN documents.is_public IS 'Whether document is publicly accessible via share link';