fix(database): enhance clearBookCache to safely manage dependencies and improve logging

---Database:clearBookCache.

function Database:clearBookCache()

    self.conn:exec("DELETE FROM book_cache")

    local sql_steps = {

        -- Clear synced/history tables that depend on book_cache_id and can be

        -- safely rebuilt on next sync.

        "DELETE FROM synced_annotations",

        "DELETE FROM synced_bookmarks",

        "DELETE FROM rating_sync_history",

        "DELETE FROM book_metadata",

        -- Keep cache rows that are still referenced by pending queues so we do

        -- not break foreign-key constraints and do not lose pending work.

        [[

            DELETE FROM book_cache

            WHERE id NOT IN (

                SELECT book_cache_id FROM pending_annotations

                UNION

                SELECT book_cache_id FROM pending_ratings

                UNION

                SELECT book_cache_id FROM pending_bookmarks

            )

        ]],

    }

    local before = self:getBookCacheStats().total

    local ok_begin, begin_res = pcall(self.conn.exec, self.conn, "BEGIN")

    if not ok_begin or begin_res ~= SQ3.OK then

        self.plugin:logErr("BookloreSync Database: clearBookCache BEGIN failed:", self.conn:errmsg())

        return false

    end

    for _, sql in ipairs(sql_steps) do

        local ok_exec, exec_res = pcall(self.conn.exec, self.conn, sql)

        if not ok_exec or exec_res ~= SQ3.OK then

            pcall(self.conn.exec, self.conn, "ROLLBACK")

            self.plugin:logErr("BookloreSync Database: clearBookCache failed:", self.conn:errmsg(), "SQL:", sql)

            return false

        end

    end

    local ok_commit, commit_res = pcall(self.conn.exec, self.conn, "COMMIT")

    if not ok_commit or commit_res ~= SQ3.OK then

        pcall(self.conn.exec, self.conn, "ROLLBACK")

        self.plugin:logErr("BookloreSync Database: clearBookCache COMMIT failed:", self.conn:errmsg())

        return false

    end

    local after = self:getBookCacheStats().total

    local cleared = math.max(0, before - after)

    if after > 0 then

        self.plugin:logInfo(

            "BookloreSync Database: Book cache cleared partially; retained",

            tostring(after),

            "rows referenced by pending queues"

        )

    else

        self.plugin:logInfo("BookloreSync Database: Book cache cleared")

    end

    self.plugin:logDbg("BookloreSync Database: clearBookCache stats", "before=", tostring(before), "after=", tostring(after), "cleared=", tostring(cleared))

    return true

end