Materials: images with captions and video support

- markdown: new directives `:::figure assets/x.png | Подпись` and
  `:::video assets/x.mp4 | Подпись` rendered as figure/figcaption and a
  video player (works with HTML escaping on); sanitizer allows video/source/
  track/figure with safe attributes only
- assets: video extensions (mp4/webm/ogg) allowed, separate limits — images
  up to 10 MB, video up to 100 MB; correct content types
- upload limits raised: web/academic multipart 120 MB per file / 200 MB per
  request, nginx client_max_body_size 200m (covers media inside ZIP imports)
- docs: new docs/06-authoring.md (markdown, images, video, assets, limits,
  import semantics); import message now says "медиафайлов"

services/academic-service/src/main/kotlin/ru/ysu/lms/academic/content/AssetStorage.kt

@@ -18,13 +18,19 @@ class AssetStorage(@Value("\${lms.content.assets-dir:/data/content-assets}") roo
     data class StoredAsset(val publicName: String, val storedPath: Path, val mime: String)
 
     fun store(originalName: String, bytes: ByteArray): StoredAsset {
-        if (bytes.size > MAX_ASSET_BYTES) {
-            throw BadRequestException("Файл $originalName слишком большой (> ${MAX_ASSET_BYTES / 1024 / 1024} МБ)")
-        }
         val ext = originalName.substringAfterLast('.', "").lowercase()
-        val allowed = setOf("png", "jpg", "jpeg", "gif", "svg", "webp")
-        if (ext !in allowed) {
-            throw BadRequestException("Недопустимый тип файла: $originalName (разрешены ${allowed.joinToString(", ")})")
+        val isVideo = ext in VIDEO_EXTENSIONS
+        val isImage = ext in IMAGE_EXTENSIONS
+        if (!isVideo && !isImage) {
+            throw BadRequestException(
+                "Недопустимый тип файла: $originalName " +
+                    "(изображения: ${IMAGE_EXTENSIONS.joinToString(", ")}; " +
+                    "видео: ${VIDEO_EXTENSIONS.joinToString(", ")})",
+            )
+        }
+        val limit = if (isVideo) MAX_VIDEO_BYTES else MAX_IMAGE_BYTES
+        if (bytes.size > limit) {
+            throw BadRequestException("Файл $originalName слишком большой (> ${limit / 1024 / 1024} МБ)")
         }
         val publicName = "${UUID.randomUUID()}.$ext"
         val target = rootDir.resolve(publicName).normalize()
@@ -50,10 +56,16 @@ class AssetStorage(@Value("\${lms.content.assets-dir:/data/content-assets}") roo
         "gif" -> "image/gif"
         "svg" -> "image/svg+xml"
         "webp" -> "image/webp"
+        "mp4" -> "video/mp4"
+        "webm" -> "video/webm"
+        "ogg", "ogv" -> "video/ogg"
         else -> "application/octet-stream"
     }
 
     private companion object {
-        const val MAX_ASSET_BYTES = 10 * 1024 * 1024
+        val IMAGE_EXTENSIONS = setOf("png", "jpg", "jpeg", "gif", "svg", "webp")
+        val VIDEO_EXTENSIONS = setOf("mp4", "webm", "ogg", "ogv")
+        const val MAX_IMAGE_BYTES = 10 * 1024 * 1024        // 10 МБ на картинку
+        const val MAX_VIDEO_BYTES = 100 * 1024 * 1024       // 100 МБ на видео
     }
 }

services/academic-service/src/main/resources/application.yml

@@ -4,6 +4,10 @@ server:
 spring:
   application:
     name: academic-service
+  servlet:
+    multipart:
+      max-file-size: 120MB
+      max-request-size: 200MB
   datasource:
     url: ${LMS_DB_URL:jdbc:postgresql://localhost:5432/lms?currentSchema=academic}
     username: ${LMS_DB_USER:lms}