feat: port remaining Vue UI surfaces with full backend support

Backend additions:
- New GORM models: NotifyChannel, PlayProfile (with PIN hashing).
- NotifyChannelService: multi-channel CRUD + unified dispatcher
  supporting Telegram / Bark / WeChat / Webhook with optional
  per-channel event filtering.
- PlayProfileService: per-user 'viewing personas' with
  content-rating gates, library scoping, PIN protection, and
  player defaults (autoplay, skip-intro, audio/subtitle prefs).
- New endpoints:
    GET    /admin/notify/channels           list
    POST   /admin/notify/channels           create
    PUT    /admin/notify/channels/:id       update
    DELETE /admin/notify/channels/:id       delete
    POST   /admin/notify/channels/:id/test  send test
    GET    /play-profiles                   list (admin: ?all=true)
    POST   /play-profiles                   create
    PUT    /play-profiles/:id               update
    DELETE /play-profiles/:id               delete
    GET    /media/recent                    home page rail
    GET    /media/stats                     library composition
    GET    /watch-history                   list
    GET    /watch-history/stats             aggregate
    GET    /watch-history/continue          continue-watching rail
    DELETE /watch-history[?media_id=]       clear
    DELETE /watch-history/:id               remove one
    GET    /discover/sections               available rails
    GET    /discover/feed?sections=a,b      multi-section TMDb fetch
    GET    /system/info                     name/version/runtime
    GET    /system/status                   uptime/cpu/mem/disk
    GET    /system/scheduler                read-only scheduler view
    GET    /stats/overview                  counts only
    GET    /stats/trend                     daily plays
    GET    /stats/top-content               most played
    GET    /stats/libraries                 per-library size
    GET    /stats/monitor                   live hardware

Frontend additions:
- New API helpers: notify_channels, play_profiles, history,
  stats_extra, media_extra, discover_extra, system.
- ProfileManagementPage (/play-profiles): full CRUD form with
  PIN management, library scoping, language preferences.
- NotifyChannelsPage (/notify-channels, admin): typed config
  forms per channel type + per-channel test action.
- SettingsPage (/settings, admin): grouped key/value editor
  covering General, Organize/Scrape, Adult, qBittorrent.
- Layout sidebar links and App.tsx routes wired for all three.

internal/handler/media_extra.go

@@ -0,0 +1,70 @@
+// Package handler — auxiliary media endpoints used by the home page
+// rails (recent additions) and the admin dashboard summary card.
+package handler
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/ShukeBta/MediaStationGo/internal/model"
+	"github.com/ShukeBta/MediaStationGo/internal/service"
+)
+
+func recentMediaHandler(svc *service.Container) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		limit, _ := strconv.Atoi(c.DefaultQuery("limit", "12"))
+		if limit <= 0 || limit > 100 {
+			limit = 12
+		}
+		var items []model.Media
+		if err := svc.Repo.DB.Order("created_at desc").Limit(limit).Find(&items).Error; err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, items)
+	}
+}
+
+func mediaStatsHandler(svc *service.Container) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		var totals struct {
+			Movies   int64 `json:"movies"`
+			TV       int64 `json:"tv"`
+			Anime    int64 `json:"anime"`
+			Music    int64 `json:"music"`
+			Unscaped int64 `json:"unscraped"`
+		}
+		// Per-library type rolls up to per-media-type via the JOIN.
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Joins("JOIN libraries ON libraries.id = media.library_id").
+			Where("libraries.type = ?", "movie").Count(&totals.Movies).Error
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Joins("JOIN libraries ON libraries.id = media.library_id").
+			Where("libraries.type = ?", "tv").Count(&totals.TV).Error
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Joins("JOIN libraries ON libraries.id = media.library_id").
+			Where("libraries.type = ?", "anime").Count(&totals.Anime).Error
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Joins("JOIN libraries ON libraries.id = media.library_id").
+			Where("libraries.type = ?", "music").Count(&totals.Music).Error
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Where("scrape_status IS NULL OR scrape_status = '' OR scrape_status = 'pending'").
+			Count(&totals.Unscaped).Error
+
+		var totalCount, totalSize, totalSeconds int64
+		_ = svc.Repo.DB.Model(&model.Media{}).Count(&totalCount).Error
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Select("COALESCE(SUM(size_bytes),0)").Row().Scan(&totalSize)
+		_ = svc.Repo.DB.Model(&model.Media{}).
+			Select("COALESCE(SUM(duration_sec),0)").Row().Scan(&totalSeconds)
+
+		c.JSON(http.StatusOK, gin.H{
+			"by_type":       totals,
+			"total":         totalCount,
+			"total_size":    totalSize,
+			"total_seconds": totalSeconds,
+		})
+	}
+}