feat: auth service + security audit fixes + cleanup legacy services

Major changes:
- Add auth-svc: JWT auth, register/login/refresh, password reset
- Add auth UI: modals, pages (/login, /register, /forgot-password)
- Add usage tracking (usage_metrics table, daily limits)
- Add tiered rate limiting (free/pro/business)
- Add LLM usage limits per tier

Security fixes:
- All repos now require userID for Update/Delete operations
- JWT middleware in chat-svc, llm-svc, agent-svc, discover-svc
- ErrNotFound/ErrForbidden errors for proper access control

Cleanup:
- Remove legacy TypeScript services/ directory
- Remove computer-svc (to be reimplemented)
- Remove old deploy/docker configs

New files:
- backend/cmd/auth-svc/main.go
- backend/internal/auth/{types,repository}.go
- backend/internal/usage/{types,repository}.go
- backend/pkg/middleware/{llm_limits,ratelimit_tiered}.go
- backend/webui/src/components/auth/*
- backend/webui/src/app/(auth)/*

Made-with: Cursor

backend/cmd/agent-svc/main.go

@@ -16,6 +16,7 @@ import (
 	"github.com/gooseek/backend/internal/search"
 	"github.com/gooseek/backend/internal/session"
 	"github.com/gooseek/backend/pkg/config"
+	"github.com/gooseek/backend/pkg/middleware"
 	"github.com/gooseek/backend/pkg/ndjson"
 )
 
@@ -69,7 +70,13 @@ func main() {
 		return c.JSON(fiber.Map{"status": "ok"})
 	})
 
-	app.Post("/api/v1/agents/search", func(c *fiber.Ctx) error {
+	agents := app.Group("/api/v1/agents", middleware.JWT(middleware.JWTConfig{
+		Secret:     cfg.JWTSecret,
+		AuthSvcURL: cfg.AuthSvcURL,
+		AllowGuest: false,
+	}))
+
+	agents.Post("/search", func(c *fiber.Ctx) error {
 		var req SearchRequest
 		if err := c.BodyParser(&req); err != nil {
 			return c.Status(400).JSON(fiber.Map{"error": "Invalid request body"})
@@ -182,6 +189,10 @@ func main() {
 		return nil
 	})
 
+	agents.Get("/status", func(c *fiber.Ctx) error {
+		return c.JSON(fiber.Map{"status": "ready", "user": middleware.GetUserID(c)})
+	})
+
 	port := cfg.AgentSvcPort
 	log.Printf("agent-svc listening on :%d", port)
 	log.Fatal(app.Listen(fmt.Sprintf(":%d", port)))