feat: Add RaidableBases plugin config module — DB migration, NestJS CRUD, Vue editor

- Migration 021: raidablebases_configs table with JSONB config_data
- Entity, module, controller (7 endpoints), service with NATS deploy/import
- Frontend: 4-tab editor (General, Difficulty, NPC, Loot & Rewards)
- Pinia store, types, router route, sidebar nav with Swords icon
- Top 30 most common settings with actual RaidableBases.json key paths
- Difficulty sub-tabs for Easy/Medium/Hard/Expert/Nightmare with spawn day toggles

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/migrations/021_raidablebases_configs.sql

@@ -0,0 +1,11 @@
+CREATE TABLE IF NOT EXISTS raidablebases_configs (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    license_id UUID NOT NULL REFERENCES licenses(id) ON DELETE CASCADE,
+    config_name VARCHAR(100) NOT NULL,
+    description TEXT,
+    config_data JSONB NOT NULL DEFAULT '{}',
+    is_active BOOLEAN NOT NULL DEFAULT false,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+CREATE INDEX idx_raidablebases_configs_license ON raidablebases_configs(license_id);