feat: add the study data models and schema migrations

Courses, meetings, class sessions, deadlines, readings with per-user
progress, materials with tags and file attachments. Timestamps are
stored in UTC and held as Europe/Warsaw text so the admin text inputs
can write them.

models/reading_progress.go

@@ -0,0 +1,17 @@
+// Code generated by summer make. DO NOT EDIT.
+
+package models
+
+import "time"
+
+// ReadingProgress records that a user (a golem15.user users row) has read a
+// reading. One row per reading and user.
+type ReadingProgress struct {
+	ID        uint      `gorm:"column:id;primaryKey"`
+	ReadingID uint      `gorm:"column:reading_id"`
+	UserID    uint      `gorm:"column:user_id"`
+	ReadAt    time.Time `gorm:"column:read_at"`
+}
+
+// TableName is the plugin table.
+func (ReadingProgress) TableName() string { return "jz_bm_reading_progress" }