UI improved

schema.sql

@@ -9,17 +9,31 @@ CREATE TABLE IF NOT EXISTS users (
     created_at    TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
 ) ENGINE=InnoDB;
 
+-- Small key/value store for app-wide facts (currently: when the last scan ran).
+CREATE TABLE IF NOT EXISTS app_meta (
+    k          VARCHAR(64) PRIMARY KEY,
+    v          VARCHAR(255) NOT NULL,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+        ON UPDATE CURRENT_TIMESTAMP
+) ENGINE=InnoDB;
+
 -- One row per directory found under VIDEOS_ROOT.
 -- `path` is the relative path from VIDEOS_ROOT, e.g. "Course 1/Intro".
+-- thumbnail_video_id/thumbnail_generated_at are only ever set on top-level
+-- (course) folders — see generateThumbnails() — and have no FK to videos
+-- (that would make folders<->videos a circular reference); a stale pointer
+-- is harmless and self-corrects on the next scan.
 CREATE TABLE IF NOT EXISTS folders (
-    id         INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-    parent_id  INT UNSIGNED NULL,
-    name       VARCHAR(255) NOT NULL,
-    path       VARCHAR(700) NOT NULL UNIQUE,
-    depth      INT UNSIGNED NOT NULL DEFAULT 0,
-    sort_order INT UNSIGNED NOT NULL DEFAULT 0,
-    is_missing TINYINT(1) NOT NULL DEFAULT 0,
-    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    id                     INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    parent_id              INT UNSIGNED NULL,
+    name                   VARCHAR(255) NOT NULL,
+    path                   VARCHAR(700) NOT NULL UNIQUE,
+    depth                  INT UNSIGNED NOT NULL DEFAULT 0,
+    sort_order             INT UNSIGNED NOT NULL DEFAULT 0,
+    is_missing             TINYINT(1) NOT NULL DEFAULT 0,
+    thumbnail_video_id     INT UNSIGNED NULL,
+    thumbnail_generated_at TIMESTAMP NULL,
+    created_at             TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
     CONSTRAINT fk_folders_parent FOREIGN KEY (parent_id)
         REFERENCES folders(id) ON DELETE CASCADE,
     INDEX idx_folders_parent (parent_id)