security(tauri): remove unused shell plugin and capability

- Remove tauri-plugin-shell from Cargo.toml
- Drop tauri_plugin_shell::init() from src-tauri/src/lib.rs
- Delete "shell:allow-open" from src-tauri/capabilities/default.json
- No runtime behavior change; opener plugin still handles links/paths
- Motivation: reduce permissions surface and slightly shrink bundle

pnpm-lock.yaml

@@ -11,9 +11,6 @@ importers:
       '@tauri-apps/api':
         specifier: ^2.8.0
         version: 2.8.0
-      '@tauri-apps/plugin-shell':
-        specifier: ^2.3.0
-        version: 2.3.0
       react:
         specifier: ^18.2.0
         version: 18.3.1
@@ -460,9 +457,6 @@ packages:
     engines: {node: '>= 10'}
     hasBin: true
 
-  '@tauri-apps/plugin-shell@2.3.0':
-    resolution: {integrity: sha512-6GIRxO2z64uxPX4CCTuhQzefvCC0ew7HjdBhMALiGw74vFBDY95VWueAHOHgNOMV4UOUAFupyidN9YulTe5xlA==}
-
   '@types/babel__core@7.20.5':
     resolution: {integrity: sha512-qoQprZvz5wQFJwMDqeseRXWv3rqMvhgpbXFfVyWhbx9X47POIA6i/+dXefEmZKoAgOaTdaIgNSMqMIU61yRyzA==}
 
@@ -970,10 +964,6 @@ snapshots:
       '@tauri-apps/cli-win32-ia32-msvc': 2.8.1
       '@tauri-apps/cli-win32-x64-msvc': 2.8.1
 
-  '@tauri-apps/plugin-shell@2.3.0':
-    dependencies:
-      '@tauri-apps/api': 2.8.0
-
   '@types/babel__core@7.20.5':
     dependencies:
       '@babel/parser': 7.28.0