fix(openclaw): remove MCP/Skills/Prompts support from OpenClaw

OpenClaw only needs provider management functionality, not MCP, Skills,
or Prompts features. This commit removes the incorrectly added support:

- Revert SCHEMA_VERSION from 6 to 5 (remove v5->v6 migration)
- Remove enabled_openclaw field from mcp_servers and skills tables
- Remove openclaw field from McpApps and SkillApps structs
- Update DAO queries to exclude enabled_openclaw column
- Fix frontend components and types to exclude openclaw from MCP/Prompts
- Update all related test files

src/components/prompts/PromptFormPanel.tsx

@@ -24,14 +24,13 @@ const PromptFormPanel: React.FC<PromptFormPanelProps> = ({
 }) => {
   const { t } = useTranslation();
   const appName = t(`apps.${appId}`);
-  const filenameMap: Record<AppId, string> = {
+  const filenameMap: Record<Exclude<AppId, "openclaw">, string> = {
     claude: "CLAUDE.md",
     codex: "AGENTS.md",
     gemini: "GEMINI.md",
     opencode: "AGENTS.md",
-    openclaw: "AGENTS.md",
   };
-  const filename = filenameMap[appId];
+  const filename = filenameMap[appId as Exclude<AppId, "openclaw">];
   const [name, setName] = useState("");
   const [description, setDescription] = useState("");
   const [content, setContent] = useState("");