feat(countries): replace Map view with browse-by-country (like Tags)

Removes the maplibre-gl Map view and adds "Countries" as a sixth
TagCategory, reusing the existing /tags/[category]/[[value]] browse
machinery instead of a bespoke map UI. Backed by a new self-contained
sidecar endpoint that aggregates photos.photo_country with BasePath
scoping, mirroring handleLabels/handleScopedCounts.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

sidecar/handlers_countries.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+// PpCountry is the country aggregation row returned to the client: a
+// 2-letter ISO 3166-1 code, the user-scoped photo count, and a representative
+// thumb hash for the sidebar row.
+type PpCountry struct {
+	Code       string `json:"Code"`
+	PhotoCount int    `json:"PhotoCount"`
+	Thumb      string `json:"Thumb"`
+}
+
+// handleCountries aggregates photos.photo_country directly against
+// PhotoPrism's DB (no upstream proxy needed — this is a simple GROUP BY)
+// and scopes the result to the caller's BasePath, mirroring handleLabels.
+//
+// Route: GET /api/sidecar/countries  (behind requireSession, ppDb != nil)
+func handleCountries(ppDb *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		basePath := ctxBasePath(c)
+
+		type countryStat struct {
+			Code      string `gorm:"column:code"`
+			Cnt       int64  `gorm:"column:cnt"`
+			ThumbHash string `gorm:"column:thumb_hash"`
+		}
+		var stats []countryStat
+
+		query := ppDb.Table("photos p").
+			Select(`p.photo_country AS code,
+			        COUNT(DISTINCT p.id) AS cnt,
+			        COALESCE(MIN(f.file_hash), '') AS thumb_hash`).
+			Joins(`LEFT JOIN files f ON f.photo_uid = p.photo_uid
+			                       AND f.file_primary = 1
+			                       AND f.file_missing = 0`).
+			Where("p.deleted_at IS NULL").
+			Where("p.photo_country != '' AND p.photo_country != 'zz'")
+
+		if basePath != "" {
+			prefix := basePath + "/%"
+			query = query.Where("(p.photo_path = ? OR p.photo_path LIKE ?)", basePath, prefix)
+		}
+
+		if err := query.
+			Group("p.photo_country").
+			Having("cnt > 0").
+			Order("cnt DESC").
+			Scan(&stats).Error; err != nil {
+			c.JSON(http.StatusBadGateway, gin.H{"error": "country stats query failed"})
+			return
+		}
+
+		out := make([]PpCountry, 0, len(stats))
+		for _, s := range stats {
+			out = append(out, PpCountry{
+				Code:       s.Code,
+				PhotoCount: int(s.Cnt),
+				Thumb:      s.ThumbHash,
+			})
+		}
+
+		c.JSON(http.StatusOK, out)
+	}
+}

sidecar/main.go

@@ -104,6 +104,7 @@ func main() {
 						if ppDb != nil {
 							auth.GET("/labels", handleLabels(pp, ppDb))
 							auth.GET("/counts", handleScopedCounts(ppDb))
+							auth.GET("/countries", handleCountries(ppDb))
 						}
 
 						// User-scoped photos — post-filters by BasePath so review/archive