feat(license): Flyway V5 — license table + environments retention columns

Per-tenant license row stores the signed token, licenseId for audit,
installed/expires/last_validated timestamps. environments gains three
INTEGER NOT NULL DEFAULT 1 retention columns (execution, log, metric)
so existing rows land inside the default-tier cap.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/main/resources/db/migration/V5__license_table_and_environment_retention.sql

@@ -0,0 +1,17 @@
+-- Per-tenant license row (one server = one tenant)
+CREATE TABLE license (
+    tenant_id         TEXT PRIMARY KEY,
+    token             TEXT NOT NULL,
+    license_id        UUID NOT NULL,
+    installed_at      TIMESTAMPTZ NOT NULL,
+    installed_by      TEXT NOT NULL,
+    expires_at        TIMESTAMPTZ NOT NULL,
+    last_validated_at TIMESTAMPTZ NOT NULL
+);
+
+-- Per-env retention; defaults to default-tier values (1 day) so a fresh
+-- server lands inside the cap without operator intervention.
+ALTER TABLE environments
+    ADD COLUMN execution_retention_days INTEGER NOT NULL DEFAULT 1,
+    ADD COLUMN log_retention_days       INTEGER NOT NULL DEFAULT 1,
+    ADD COLUMN metric_retention_days    INTEGER NOT NULL DEFAULT 1;