fix(server): revert migration 008 comment edit — modifying an applied sqlx migration breaks its checksum and crash-loops the server on startup; machines.rs ON CONFLICT fix retained

server/migrations/008_machine_uid.sql

@@ -34,12 +34,8 @@ ALTER TABLE connect_machines ADD COLUMN IF NOT EXISTS machine_uid TEXT;
 
 -- 2. Enforce one row per machine_uid, but ONLY for rows that actually have one.
 --    A partial UNIQUE index (WHERE machine_uid IS NOT NULL) lets unlimited legacy
---    NULL rows coexist while making a non-null machine_uid a true dedup key. Because
---    this index is PARTIAL, Postgres only binds an ON CONFLICT inference clause to it
---    when the clause REPEATS the same predicate: upsert_machine's arbiter must be
---    `ON CONFLICT (machine_uid) WHERE machine_uid IS NOT NULL` (a bare
---    `ON CONFLICT (machine_uid)` raises "no unique or exclusion constraint matching
---    the ON CONFLICT specification" at runtime and persists no row).
+--    NULL rows coexist while making a non-null machine_uid a true dedup key — this
+--    is what upsert_machine's `ON CONFLICT (machine_uid)` arbiter binds to.
 CREATE UNIQUE INDEX IF NOT EXISTS idx_connect_machines_machine_uid
     ON connect_machines (machine_uid)
     WHERE machine_uid IS NOT NULL;