fix(db): swap conversation_keys natural PK for synthetic row_id

Migration 20260515000002 failed on prod because dropping NOT NULL on
recipient_device_id was rejected (column is part of the natural primary
key). This fix-up drops the PK, adds a synthetic row_id BIGSERIAL PK,
re-applies the NOT NULL drop, and re-runs the indexes/policies that
were skipped after the failure.

supabase/migrations/20260515000005_conversation_keys_pk_fix.sql

@@ -0,0 +1,89 @@
+-- Fix-up for failed 20260515000002: dropping NOT NULL on a PK column requires
+-- dropping the PK first. Replace the natural PK (conversation_id,
+-- recipient_device_id, key_version) with a synthetic row_id and re-establish
+-- uniqueness via two partial unique indexes — one per recipient mode.
+--
+-- Also re-runs the policies + indexes from 20260515000002 that were skipped
+-- when migration 2 errored out at the ALTER COLUMN step.
+
+alter table public.conversation_keys
+  drop constraint if exists conversation_keys_pkey;
+
+alter table public.conversation_keys
+  add column if not exists row_id bigserial primary key;
+
+alter table public.conversation_keys
+  alter column recipient_device_id drop not null,
+  alter column sender_device_id    drop not null;
+
+-- Partial unique constraints: device-mode and user-mode rows can coexist for
+-- the same (conv, version) but each mode is unique on its own.
+create unique index if not exists conversation_keys_device_recipient_uniq
+  on public.conversation_keys(conversation_id, recipient_device_id, key_version)
+  where recipient_device_id is not null;
+
+create unique index if not exists conversation_keys_user_recipient_uniq
+  on public.conversation_keys(conversation_id, recipient_user_id, key_version)
+  where recipient_user_id is not null;
+
+create index if not exists conversation_keys_recipient_user_idx
+  on public.conversation_keys(recipient_user_id);
+
+-- Re-apply the policies from migration 20260515000002 (those didn't run
+-- because the failing ALTER stopped the file).
+drop policy if exists conversation_keys_select_owner on public.conversation_keys;
+create policy conversation_keys_select_owner
+  on public.conversation_keys
+  for select
+  to authenticated
+  using (
+    recipient_user_id = auth.uid()
+    or exists (
+      select 1
+        from public.devices d
+       where d.id = recipient_device_id
+         and d.user_id = auth.uid()
+    )
+  );
+
+drop policy if exists conversation_keys_insert_member on public.conversation_keys;
+create policy conversation_keys_insert_member
+  on public.conversation_keys
+  for insert
+  to authenticated
+  with check (
+    exists (
+      select 1
+        from public.conversation_members m
+       where m.conversation_id = conversation_keys.conversation_id
+         and m.user_id = auth.uid()
+         and m.accepted = true
+    )
+    and (
+      sender_user_id = auth.uid()
+      or exists (
+        select 1
+          from public.devices d
+         where d.id = sender_device_id
+           and d.user_id = auth.uid()
+      )
+    )
+    and (
+      (recipient_user_id is not null and exists (
+        select 1
+          from public.conversation_members m
+         where m.conversation_id = conversation_keys.conversation_id
+           and m.user_id = recipient_user_id
+           and m.accepted = true
+      ))
+      or (recipient_device_id is not null and exists (
+        select 1
+          from public.devices d
+          join public.conversation_members m
+            on m.user_id = d.user_id
+           and m.conversation_id = conversation_keys.conversation_id
+         where d.id = recipient_device_id
+           and m.accepted = true
+      ))
+    )
+  );