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-tauri/src/mcp/claude.rs

@@ -92,7 +92,6 @@ pub fn import_from_claude(config: &mut MultiAppConfig) -> Result<usize, AppError
                         codex: false,
                         gemini: false,
                         opencode: false,
-                        openclaw: false,
                     },
                     description: None,
                     homepage: None,

src-tauri/src/mcp/codex.rs

@@ -236,7 +236,6 @@ pub fn import_from_codex(config: &mut MultiAppConfig) -> Result<usize, AppError>
                             codex: true,
                             gemini: false,
                             opencode: false,
-                            openclaw: false,
                         },
                         description: None,
                         homepage: None,

src-tauri/src/mcp/gemini.rs

@@ -88,7 +88,6 @@ pub fn import_from_gemini(config: &mut MultiAppConfig) -> Result<usize, AppError
                         codex: false,
                         gemini: true,
                         opencode: false,
-                        openclaw: false,
                     },
                     description: None,
                     homepage: None,

src-tauri/src/mcp/opencode.rs

@@ -259,7 +259,6 @@ pub fn import_from_opencode(config: &mut MultiAppConfig) -> Result<usize, AppErr
                         codex: false,
                         gemini: false,
                         opencode: true,
-                        openclaw: false,
                     },
                     description: None,
                     homepage: None,