Initial commit: LlamaLink Go rewrite

Complete rewrite from Python/FastAPI to Go/Gin:
- Go backend: auth (API keys + bcrypt), llama.cpp subprocess manager,
  hot-swap multi-model, rate limiting, quota system, webhooks
- Vue 3 SPA admin panel (src/) with Tailwind CSS
- Deployment: Docker multi-stage, docker-compose, nginx, systemd
- GORM/SQLite models: ApiKey, Model, UsageLog, Quota, Webhook
- REST API: /api/v1/admin/* (keys, models, chat, usage, health)
- Embedded frontend via go:embed (build output at web/dist/)

Removed legacy Python artifacts (app/, tests/, pyproject.toml, etc.)

internal/api/middleware/auth.go

@@ -0,0 +1,156 @@
+package middleware
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"github.com/llamalink/llamalink/internal/auth"
+	"github.com/llamalink/llamalink/internal/db"
+)
+
+const (
+	ApiKeyCtx   = "api_key"
+	ApiKeyIDCtx = "api_key_id"
+)
+
+func APIKeyAuth(authService *auth.Service) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		authHeader := c.GetHeader("Authorization")
+		if authHeader == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": gin.H{
+					"code":    "invalid_api_key",
+					"message": "Authorization header required",
+				},
+			})
+			return
+		}
+
+		token := strings.TrimPrefix(authHeader, "Bearer ")
+		if token == authHeader {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": gin.H{
+					"code":    "invalid_api_key",
+					"message": "Bearer token required",
+				},
+			})
+			return
+		}
+
+		apiKey, err := authService.Validate(token)
+		if err != nil {
+			code := "invalid_api_key"
+			status := http.StatusUnauthorized
+			if err == auth.ErrKeyRevoked || err == auth.ErrKeyExpired {
+				code = "api_key_revoked"
+				status = http.StatusUnauthorized
+			}
+
+			c.AbortWithStatusJSON(status, gin.H{
+				"error": gin.H{
+					"code":    code,
+					"message": err.Error(),
+				},
+			})
+			return
+		}
+
+		c.Set(ApiKeyCtx, apiKey)
+		c.Set(ApiKeyIDCtx, apiKey.ID)
+		c.Next()
+	}
+}
+
+func RequireScope(authService *auth.Service, scope string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		apiKey, exists := c.Get(ApiKeyCtx)
+		if !exists {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": gin.H{
+					"code":    "invalid_api_key",
+					"message": "Authentication required",
+				},
+			})
+			return
+		}
+
+		key := apiKey.(*db.ApiKey)
+		if !authService.HasScope(key, scope) {
+			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{
+				"error": gin.H{
+					"code":    "insufficient_scope",
+					"message": "API key lacks required scope: " + scope,
+				},
+			})
+			return
+		}
+
+		c.Next()
+	}
+}
+
+func AdminOnly() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		apiKey, exists := c.Get(ApiKeyCtx)
+		if !exists {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": gin.H{
+					"code":    "unauthorized",
+					"message": "Admin access required",
+				},
+			})
+			return
+		}
+
+		key := apiKey.(*db.ApiKey)
+		if !key.IsAdmin {
+			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{
+				"error": gin.H{
+					"code":    "unauthorized",
+					"message": "Admin access required",
+				},
+			})
+			return
+		}
+
+		c.Next()
+	}
+}
+
+func AdminTokenAuth(token string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		adminToken := c.GetHeader("X-Admin-Token")
+		if adminToken == "" {
+			adminToken = c.GetHeader("Authorization")
+			adminToken = strings.TrimPrefix(adminToken, "Bearer ")
+		}
+
+		if adminToken != token {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error": gin.H{
+					"code":    "unauthorized",
+					"message": "Invalid admin token",
+				},
+			})
+			return
+		}
+
+		c.Next()
+	}
+}
+
+func GetAPIKeyID(c *gin.Context) uuid.UUID {
+	id, _ := c.Get(ApiKeyIDCtx)
+	return id.(uuid.UUID)
+}
+
+func GetAPIKey(c *gin.Context) *db.ApiKey {
+	key, _ := c.Get(ApiKeyCtx)
+	if key == nil {
+		return nil
+	}
+	return key.(*db.ApiKey)
+}