OIDC: local HTTP server instead of Wails bindings

The Wails runtime isn't reliably loading for IPC calls. Replace the
binding-based StartOIDCLogin with a local HTTP server on 127.0.0.1:18901:

- /oidc/login?apiUrl=... — opens system browser, waits for token
- /oidc/callback — Authentik redirect target, exchanges code
- /oidc/config?apiUrl=... — fetches OIDC provider config
- SPA detects desktop via ?desktop=1 URL param
- SPA calls localhost directly via fetch() instead of Wails IPC

web/src/pages/Config.svelte

@@ -68,21 +68,25 @@
     oidcLoggingIn = true
     setConfig({ apiUrl: apiUrl.trim(), token: '' })
 
-    const wails = (window as any).wails
-    if (wails?.Call?.ByName) {
+    const isDesktop = new URLSearchParams(location.search).has('desktop')
+
+    if (isDesktop) {
       try {
-        const token = await wails.Call.ByName('StartOIDCLogin', apiUrl.trim())
-        if (token) {
-          setConfig({ apiUrl: apiUrl.trim(), token })
-          initConfig({ apiUrl: apiUrl.trim(), token })
+        const resp = await fetch(`http://127.0.0.1:18901/oidc/login?apiUrl=${encodeURIComponent(apiUrl.trim())}`)
+        const data = await resp.json()
+        if (data.token) {
+          setConfig({ apiUrl: apiUrl.trim(), token: data.token })
+          initConfig({ apiUrl: apiUrl.trim(), token: data.token })
+          oidcLoggingIn = false
           onConnected()
           return
         }
+        error = data.error || 'Login failed'
       } catch (e: any) {
-        error = e?.message || e || 'OIDC login failed'
-        oidcLoggingIn = false
-        return
+        error = e.message || 'Could not reach OIDC service'
       }
+      oidcLoggingIn = false
+      return
     }
 
     try {