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/ratelimit.go

@@ -0,0 +1,85 @@
+package middleware
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"golang.org/x/time/rate"
+)
+
+type RateLimiter struct {
+	visitors map[string]*visitor
+	mu       sync.RWMutex
+	rate     rate.Limit
+	burst    int
+}
+
+type visitor struct {
+	limiter  *rate.Limiter
+	lastSeen time.Time
+}
+
+func NewRateLimiter(requestsPerMinute int) *RateLimiter {
+	rl := &RateLimiter{
+		visitors: make(map[string]*visitor),
+		rate:     rate.Limit(float64(requestsPerMinute) / 60.0),
+		burst:    requestsPerMinute / 10,
+	}
+	if requestsPerMinute < 10 {
+		rl.burst = 1
+	}
+
+	// Cleanup old visitors
+	go rl.cleanup()
+
+	return rl
+}
+
+func (rl *RateLimiter) cleanup() {
+	ticker := time.NewTicker(5 * time.Minute)
+	for range ticker.C {
+		rl.mu.Lock()
+		for ip, v := range rl.visitors {
+			if time.Since(v.lastSeen) > 10*time.Minute {
+				delete(rl.visitors, ip)
+			}
+		}
+		rl.mu.Unlock()
+	}
+}
+
+func (rl *RateLimiter) getVisitor(ip string) *rate.Limiter {
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+
+	v, exists := rl.visitors[ip]
+	if !exists {
+		v = &visitor{
+			limiter:  rate.NewLimiter(rl.rate, rl.burst),
+			lastSeen: time.Now(),
+		}
+		rl.visitors[ip] = v
+	}
+
+	v.lastSeen = time.Now()
+	return v.limiter
+}
+
+func RateLimitMiddleware(rl *RateLimiter) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		ip := c.ClientIP()
+		if !rl.getVisitor(ip).Allow() {
+			c.AbortWithStatusJSON(http.StatusTooManyRequests, gin.H{
+				"error": gin.H{
+					"code":             "rate_limit_exceeded",
+					"message":          "Too many requests",
+					"retry_after_seconds": 60,
+				},
+			})
+			return
+		}
+		c.Next()
+	}
+}