add email threads to companies

src/db/migrations/0008_add_company_id_to_emails.sql

@@ -0,0 +1,20 @@
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM information_schema.columns
+        WHERE table_name = 'emails' AND column_name = 'company_id'
+    ) THEN
+        ALTER TABLE emails
+        ADD COLUMN company_id UUID REFERENCES companies(id) ON DELETE SET NULL;
+    END IF;
+END $$;
+
+CREATE INDEX IF NOT EXISTS idx_emails_company_id ON emails(company_id);
+CREATE INDEX IF NOT EXISTS idx_emails_company_thread ON emails(company_id, thread_id);
+
+UPDATE emails e
+SET company_id = c.company_id
+FROM contacts c
+WHERE e.contact_id = c.id
+  AND c.company_id IS NOT NULL
+  AND (e.company_id IS NULL OR e.company_id <> c.company_id);