Add GeminiModels handler and enhance API key validation

- Introduced `GeminiModels` handler to serve Gemini model information under `/v1beta/models`.
- Updated `AuthMiddleware` to validate API keys from query parameters for improved flexibility.
- Adjusted route to use the new handler for model retrieval.

internal/api/gemini-handlers.go

@@ -14,6 +14,22 @@ import (
 	"time"
 )
 
+func (h *APIHandlers) GeminiModels(c *gin.Context) {
+	c.Status(200)
+	c.Header("Content-Type", "application/json; charset=UTF-8")
+	_, _ = c.Writer.Write([]byte(`{"models":[{"name":"models/gemini-2.5-flash","version":"001","displayName":"Gemini `))
+	_, _ = c.Writer.Write([]byte(`2.5 Flash","description":"Stable version of Gemini 2.5 Flash, our mid-size multimod`))
+	_, _ = c.Writer.Write([]byte(`al model that supports up to 1 million tokens, released in June of 2025.","inputTok`))
+	_, _ = c.Writer.Write([]byte(`enLimit":1048576,"outputTokenLimit":65536,"supportedGenerationMethods":["generateCo`))
+	_, _ = c.Writer.Write([]byte(`ntent","countTokens","createCachedContent","batchGenerateContent"],"temperature":1,`))
+	_, _ = c.Writer.Write([]byte(`"topP":0.95,"topK":64,"maxTemperature":2,"thinking":true},{"name":"models/gemini-2.`))
+	_, _ = c.Writer.Write([]byte(`5-pro","version":"2.5","displayName":"Gemini 2.5 Pro","description":"Stable release`))
+	_, _ = c.Writer.Write([]byte(` (June 17th, 2025) of Gemini 2.5 Pro","inputTokenLimit":1048576,"outputTokenLimit":`))
+	_, _ = c.Writer.Write([]byte(`65536,"supportedGenerationMethods":["generateContent","countTokens","createCachedCo`))
+	_, _ = c.Writer.Write([]byte(`ntent","batchGenerateContent"],"temperature":1,"topP":0.95,"topK":64,"maxTemperatur`))
+	_, _ = c.Writer.Write([]byte(`e":2,"thinking":true}],"nextPageToken":""}`))
+}
+
 func (h *APIHandlers) GeminiHandler(c *gin.Context) {
 	var person struct {
 		Action string `uri:"action" binding:"required"`