Add PocketBase schema migrations and migration pipeline

- 8 collections: vereine, gruppen, mitglieder, beitraege, einzuege,
  termine, nachrichten, push_subscriptions
- verein_id relation added to users (multi-tenant isolation)
- API rules enforce tenant separation via @request.auth.verein_id
- docker-compose: --migrationsDir=/pb_data/migrations flag + volume mount
- Makefile: migrations sync step added to deploy target

Makefile

@@ -18,8 +18,10 @@ TAR_EXCLUDE := --exclude='.git' \
                --exclude='./.env' \
                --exclude='./.DS_Store'
 
-HOOKS_SRC := pocketbase/pb_hooks
-HOOKS_DST := /volume1/docker/vereinshaus/pocketbase/data/pb_hooks
+HOOKS_SRC      := pocketbase/pb_hooks
+HOOKS_DST      := /volume1/docker/vereinshaus/pocketbase/data/pb_hooks
+MIGRATIONS_SRC := pocketbase/pb_migrations
+MIGRATIONS_DST := /volume1/docker/vereinshaus/pocketbase/migrations
 
 .PHONY: help check-ssh start stop restart status logs logs-f logs-app \
         shell-pb pb-admin deploy
@@ -71,6 +73,13 @@ deploy: check-ssh
 			cat "$$f" | ssh $(DS_HOST) "cat > $(HOOKS_DST)/$$(basename $$f)"; \
 		done; \
 	fi
+	@echo "→ PocketBase Migrations synchronisieren..."
+	@ssh $(DS_HOST) "mkdir -p $(MIGRATIONS_DST)"
+	@if ls $(MIGRATIONS_SRC)/*.js 2>/dev/null | grep -q .; then \
+		for f in $(MIGRATIONS_SRC)/*.js; do \
+			cat "$$f" | ssh $(DS_HOST) "cat > $(MIGRATIONS_DST)/$$(basename $$f)"; \
+		done; \
+	fi
 	@echo "→ Docker rebuild + restart..."
 	@ssh $(DS_HOST) " \
 		cd $(DS_PATH) && \