Add gallery admin and video media support.

This updates gallery handling to support video playback with generated poster thumbnails, adds authenticated admin upload/delete flows, and improves dev/runtime behavior including reliable thumbnail generation and media-safe response handling.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -13,15 +13,13 @@ RUN templ generate && CGO_ENABLED=0 go build -ldflags="-s -w" -o /server ./cmd/s
 FROM debian:bookworm-slim
 
 RUN apt-get update \
-	&& apt-get install -y --no-install-recommends ca-certificates \
+	&& apt-get install -y --no-install-recommends ca-certificates ffmpeg \
 	&& rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
 
 COPY --from=builder /server ./server
 COPY app/static ./static
-COPY app/images ./images
-RUN ./server -thumbs
 
 EXPOSE 8080
 ENV ADDR=:8080