feat(early-access): implement EA filtering and UI improvements

Add Early Access version support with filtering and improved UI:

Backend:
- Add is_early_access and early_access_ends_at fields to ModelVersionRecord
- Implement two-phase EA detection (bulk API + single API enrichment)
- Add hide_early_access_updates setting to filter EA updates
- Update has_update() and has_updates_bulk() to respect EA filter setting
- Add _enrich_early_access_details() for precise EA time fetching
- Fix setting propagation through base_model_service and model_update_service

Frontend:
- Add smart relative time display for EA (in Xh, in Xd, or date)
- Replace EA label with clock icon in metadata (fa-clock)
- Show Download button with bolt icon for EA versions (fa-bolt)
- Change EA badge color to #F59F00 (CivitAI Buzz theme)
- Fix toggle UI for hide_early_access_updates setting
- Add translation keys for EA time formatting

Tests:
- Update all tests to pass with new EA functionality
- Add test coverage for EA filtering logic

Closes #815

locales/zh-CN.json

@@ -426,6 +426,10 @@
                 "any": "显示任何可用更新"
             }
         },
+        "hideEarlyAccessUpdates": {
+            "label": "[TODO: Translate] Hide Early Access Updates",
+            "help": "[TODO: Translate] When enabled, models with only early access updates will not show 'Update available' badge"
+        },
         "misc": {
             "includeTriggerWords": "复制 LoRA 语法时包含触发词",
             "includeTriggerWordsHelp": "复制 LoRA 语法到剪贴板时包含训练触发词"
@@ -1031,12 +1035,19 @@
                 },
                 "labels": {
                     "unnamed": "未命名版本",
-                    "noDetails": "暂无更多信息"
+                    "noDetails": "暂无更多信息",
+                    "earlyAccess": "[TODO: Translate] Early Access"
+                },
+                "eaTime": {
+                    "endingSoon": "[TODO: Translate] ending soon",
+                    "hours": "[TODO: Translate] in {count}h",
+                    "days": "[TODO: Translate] in {count}d"
                 },
                 "badges": {
                     "current": "当前版本",
                     "inLibrary": "已在库中",
                     "newer": "较新的版本",
+                    "earlyAccess": "[TODO: Translate] Early Access",
                     "ignored": "已忽略"
                 },
                 "actions": {
@@ -1044,6 +1055,7 @@
                     "delete": "删除",
                     "ignore": "忽略",
                     "unignore": "取消忽略",
+                    "earlyAccessTooltip": "[TODO: Translate] Requires early access purchase",
                     "resumeModelUpdates": "继续跟踪该模型的更新",
                     "ignoreModelUpdates": "忽略该模型的更新",
                     "viewLocalVersions": "查看所有本地版本",