feat: promote accepted proposals from API

server/migrations/0005_proposal_match_plans.sql

@@ -0,0 +1,15 @@
+-- Preserve the matcher-selected topology through the proposal response window.
+-- These fields are nullable for already-created proposals during a rolling
+-- deployment; new matcher-created proposals always populate them before they
+-- can be promoted to an ALLOCATING match.
+ALTER TABLE proposals
+    ADD COLUMN match_region TEXT CHECK (match_region IN ('EU', 'NA')),
+    ADD COLUMN match_protocol INTEGER CHECK (match_protocol > 0);
+
+ALTER TABLE proposal_participants
+    ADD COLUMN team INTEGER CHECK (team IN (0, 1)),
+    ADD COLUMN slot INTEGER CHECK (slot BETWEEN 0 AND 5);
+
+CREATE UNIQUE INDEX proposal_participants_unique_slot
+    ON proposal_participants (proposal_id, slot)
+    WHERE slot IS NOT NULL;