Fix Google API key validation to accept new key formats (#1581)

Google now issues API keys starting with "AQ" in addition to the legacy
"AIza" prefix. Remove the prefix constraint for Gemini and keep only a
minimum length check (30 chars) so both key formats are accepted.

https://claude.ai/code/session_01JA1bi4mmwBEm8A2WAFCid4

Co-authored-by: Claude <noreply@anthropic.com>

Author: SebConejo

packages/frontend/src/services/providers.ts

@@ -109,9 +109,9 @@ export const PROVIDERS: ProviderDef[] = [
     color: '#4285f4',
     initial: 'G',
     subtitle: 'Gemini 2.5, Gemini 2.0 Flash',
-    keyPrefix: 'AIza',
-    minKeyLength: 39,
-    keyPlaceholder: 'AIza...',
+    keyPrefix: '',
+    minKeyLength: 30,
+    keyPlaceholder: 'API key',
     models: [],
   },
   {