feat(books): support reviews, rating removal, and plugin enhancements

Add support for user-scoped personal notes (reviews) and allow clearing book ratings to null,
providing full sync capabilities for these actions in the KOReader plugin. Modularize the
KOReader plugin codebase into dedicated mixin files to improve maintainability and expand
the catalog detail view with related sections (series, author, similar books).

Closes #552

koreader-plugin/bookorbit.koplugin/bookorbit_stats_reader.lua

@@ -126,6 +126,48 @@ function BookOrbitStatsReader.getBookIds(md5)
     return result or {}
 end
 
+-- Aggregated local reading activity for the dashboard stats strip: seconds
+-- read today and over the past 7 days, plus the current daily reading streak
+-- (consecutive days with any reading, still counting if today has none yet).
+function BookOrbitStatsReader.getReadingSummary()
+    return withConn(function(conn)
+        local today = os.date("*t")
+        today.hour, today.min, today.sec = 0, 0, 0
+        local day_start = os.time(today)
+        local function sumSince(start_time)
+            local res = conn:exec(string.format(
+                "SELECT COALESCE(SUM(MIN(duration, 86400)), 0) FROM page_stat_data WHERE start_time >= %d;",
+                start_time))
+            return res and tonumber(res[1][1]) or 0
+        end
+
+        local streak = 0
+        local res = conn:exec(string.format(
+            "SELECT DISTINCT date(start_time, 'unixepoch', 'localtime') FROM page_stat_data WHERE start_time >= %d;",
+            day_start - 366 * 86400))
+        if res then
+            local days = {}
+            for i = 1, #res[1] do
+                days[res[1][i]] = true
+            end
+            local cursor = day_start
+            if not days[os.date("%Y-%m-%d", cursor)] then
+                cursor = cursor - 86400
+            end
+            while days[os.date("%Y-%m-%d", cursor)] do
+                streak = streak + 1
+                cursor = cursor - 86400
+            end
+        end
+
+        return {
+            today_seconds = sumSince(day_start),
+            week_seconds = sumSince(day_start - 6 * 86400),
+            streak_days = streak,
+        }
+    end)
+end
+
 -- Returns events newer than the watermark across all stat row ids of a book,
 -- ordered by start_time. The caller handles batching via the limit.
 function BookOrbitStatsReader.getEventsAfter(ids, watermark, limit)