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

web/src/lib/i18n/en.json

@@ -3,6 +3,9 @@
     "name": "Tinyforge",
     "version": "v0.1"
   },
+  "layout": {
+    "serviceStatus": "Service status"
+  },
   "health": {
     "connected": "connected",
     "disconnected": "disconnected",
@@ -56,6 +59,7 @@
     "windowMinutes": "{n} minutes",
     "windowHours": "{n} hours",
     "noSamples": "No samples yet — the collector samples every {interval}s.",
+    "collectionDisabled": "Stats collection is disabled. Enable it in Settings to populate this chart.",
     "diskImages": "Images",
     "diskContainers": "Containers",
     "diskVolumes": "Volumes",
@@ -949,7 +953,11 @@
     "dockerHint": "Check that the Docker daemon is running and that the socket is reachable.",
     "proxyHint": "Verify the proxy URL, credentials, and that the service is listening.",
     "noProxyDesc": "No proxy provider is configured. Tinyforge can manage routes via Nginx Proxy Manager or Traefik.",
-    "configureProxy": "Configure in Settings"
+    "configureProxy": "Configure in Settings",
+    "dockerNotReachable": "Docker daemon is not reachable.",
+    "dockerUnreachable": "Docker unreachable",
+    "proxyUnreachable": "Proxy unreachable",
+    "reachable": "reachable"
   },
   "dns": {
     "title": "DNS Records",