fix: harden security, fix concurrency bugs, and address review findings

Security:
- rate limit /api/webhook routes per-IP and cap concurrent site syncs
- global SSE connection cap (256) with new sse_gate
- validate ?tail= and cap JSON log responses at 4 MiB
- strip ANSI/CSI/OSC and control bytes from streamed log lines
- redact webhook secret from request log middleware
- scrub host details from /api/health for non-admin viewers
- drop container_id from /api/system/stats/top for non-admins
- generate webhook secrets via crypto/rand; require >=32 chars on insert
- verify iid path consistency in streamContainerLogs
- LimitReader on site webhook body; reject malformed non-empty bodies

Concurrency / correctness:
- stats collector: Stop() no longer hangs without Start(), semaphore
  acquired in parent loop so ctx cancellation short-circuits the queue,
  in-flight tick cancellable via shared base context, zero-ts guard
- webhook handler: replace fire-and-forget goroutine with WaitGroup-tracked
  workers + Drain() wired into graceful shutdown
- $derived(() => ...) mis-idiom fixed in ContainerStats / InstanceCard /
  ProjectCard (returned function instead of value)
- SystemResourcesCard: rename `window` and `t` locals to avoid shadowing
  globalThis.window and the i18n `t` import

Quality / performance:
- replace O(n^2) insertion sort with sort.Slice in stats top
- runMigrations only swallows duplicate-column / already-exists errors
- PruneStatsSamplesBefore wrapped in a transaction
- collapse N+1 in unusedImageStats / pruneImages to one ListAllInstances
  pass; surface DB errors instead of silently treating them as inactive
- run Docker Info + DiskUsage in parallel via errgroup
- container log SSE emits `: ping` heartbeat every 20 s
- imageMatches case-insensitive on registry host (RFC behaviour)
- log warning on invalid stage tag pattern instead of silent skip
- reject malformed non-empty site webhook payloads

Frontend / i18n:
- shared formatBytes utility replaces three local copies
- statsInterval store drives dynamic "no samples / collection disabled"
  copy across ContainerStats and SystemResourcesCard
- top consumers row now shows owner_name (project/stage or site name)
- drop seven `as any` casts on the Settings type; add cloudflare_api_token
  write-only field
- move "Service status", "Docker daemon", "Docker unreachable",
  "Proxy unreachable", "reachable", and "Docker daemon is not reachable."
  strings into en/ru i18n bundles

internal/api/webhooks.go

@@ -1,16 +1,28 @@
 package api
 
 import (
+	"crypto/rand"
+	"encoding/hex"
 	"errors"
 	"log/slog"
 	"net/http"
 
 	"github.com/go-chi/chi/v5"
-	"github.com/google/uuid"
 
 	"github.com/alexei/tinyforge/internal/store"
 )
 
+// generateWebhookSecret returns a 256-bit hex-encoded random token. Mirrors
+// the helper in internal/store; kept here to avoid an import cycle and so the
+// rotation handlers don't pretend to use uuid for what is really a secret.
+func generateWebhookSecret() string {
+	b := make([]byte, 32)
+	if _, err := rand.Read(b); err != nil {
+		panic("crypto/rand failed: " + err.Error())
+	}
+	return hex.EncodeToString(b)
+}
+
 // webhookURLResponse is the common payload returned by every webhook endpoint.
 // Clients never see raw secrets except at issue/rotate time via these fields;
 // the URL shape is "/api/webhook/..." so callers can prepend their own origin.
@@ -58,7 +70,7 @@ func (s *Server) regenerateProjectWebhook(w http.ResponseWriter, r *http.Request
 		return
 	}
 
-	secret := uuid.New().String()
+	secret := generateWebhookSecret()
 	if err := s.store.SetProjectWebhookSecret(id, secret); err != nil {
 		slog.Error("regenerate project webhook: set secret", "project", id, "error", err)
 		respondError(w, http.StatusInternalServerError, "failed to rotate webhook secret")
@@ -107,7 +119,7 @@ func (s *Server) regenerateStaticSiteWebhook(w http.ResponseWriter, r *http.Requ
 		return
 	}
 
-	secret := uuid.New().String()
+	secret := generateWebhookSecret()
 	if err := s.store.SetStaticSiteWebhookSecret(id, secret); err != nil {
 		slog.Error("regenerate site webhook: set secret", "site", id, "error", err)
 		respondError(w, http.StatusInternalServerError, "failed to rotate webhook secret")